Chrystelle N H Atinkpahoun

Marie-Noëlle Pons

Pauline Louis

Jean-Pierre Leclerc

Henri H Soclo

RARE EARTH ELEMENTS (REE) IN THE URBAN WASTEWATER OF COTONOU (BENIN, WEST AFRICA)

Keywords: Drinking water, Gadolinium, Rare-earth elements, Wastewater, Well water

The rare earth element (REE) contamination of urban wastewater, which was collected from open sewers and the inlet of a wastewater treatment plant in Cotonou (Benin), was assessed. The drinking water distributed to the inhabitants of Cotonou and water samples from private wells were also analyzed. The sampling occurred between October and December 2016 and the samples were analyzed by ICP-MS. Although the only magnetic resonance imaging facility in Cotonou opened in November 2016, pollution by anthropogenic gadolinium (Gd), which is included in phase contrast agents, was observed: there was 30 to 620 times more Gd in wastewater samples than in drinking and well water samples. Europium was another REE presenting positive anomalies. It is hypothetized than the europium came from the leachates of solid waste piles in the street. In the absence of any wastewater treatment, the REEs found in the wastewater are spread to the aquatic environment. It would be interesting to monitor the wastewater REEs over the long term. So far, the aquifers used for water provision have not been polluted by the anthropogenic REEs.

INTRODUCTION

Accessibility to clean water for all is one of the 17 millennium development goals (MDGs) set by UNO in 2015 in its 2030 agenda for sustainable development ( UN-water, 2017). This goal implies the improvement of sanitation infrastructure and control in many countries. [START_REF] Wang | Water and wastewater treatment in Africa -Current practices and challenges[END_REF] reviewed the gaps in the current practices for water and wastewater treatment in Africa, as well as the efforts needed to achieve the MDGs. These authors insisted on the insufficient infrastructure and the poor operation and maintenance of sewerage systems. The situation is worsened by rapid, ongoing urbanization and climate change [START_REF] Koop | The challenges of water, waste and climate change in cities[END_REF].

According to the UN-Water report (2017), on average, high-income countries treat approximately 70% of the municipal and industrial wastewater they generate. That percentage drops to 38% in upper-middle-income countries (15% of African countries) and to 28% in lower-middle-income countries (33% of African countries). In low-income countries (50% of African countries), only 8% of the municipal and industrial wastewater undergoes treatment of any kind before it is discharged into the aquatic environment.

Sanitation primarily concerns the removal or degradation of macropollutants, such as suspended matter, organic matter and nutrients (nitrogen, phosphorus), whose concentrations are increased by human activities. However, micropollutants that are toxic at low doses should also be addressed. According to [START_REF] Sibanda | Urban effluent discharges as causes of public and environmental health concerns in South Africa's aquatic milieu[END_REF], the quality of South African aquatic ecosystems is deteriorating not only due to the discharge of macropollutants and pathogens (as also stressed by Luyt et al., 2012, Singh and[START_REF] Singh | Microbiological, coliphages and physicochemical assessments of the Umgeni River, South Africa[END_REF] but also due to the presence of metals and endocrine-disrupting compounds (EDCs). Metals in water systems can have a natural or anthropogenic origin, and those of anthropogenic ones can originate from domestic [START_REF] Atinkpahoun | Population mobility and urban wastewater dynamics[END_REF], industrial etc. sources (e.g., mining [START_REF] Affum | Influence of small-scale gold mining and toxic element concentrations in Bonsa River, Ghana: a potential risk to water quality and public health[END_REF][START_REF] Du Preez | Metal enrichment and contamination in a karst cave associated with anthropogenic activities in the Witwatersrand Basin, South Africa[END_REF][START_REF] Olias | Temporal variations of REE in several AMD sources of the Odiel River (SW Spain)[END_REF][START_REF] Atibu | High contamination in the areas surrounding abandoned mines and mining activities: An impact assessment of the Dilala, Luilu and Mpingiri Rivers, Democratic Republic of the Congo[END_REF] or metal factories [START_REF] Belabed | Modeling seasonal and spatial contamination of surface waters and upper sediments with trace metal elements across industrialized urban areas of the Seybouse watershed in North Africa[END_REF]). They can be directly ingested by humans through drinking water [START_REF] Elumalai | Human exposure risk assessment due to heavy metals in groundwater by pollution index and multivariate statistical methods: A case study from South Africa[END_REF] or indirectly ingested by the consumption of freshwater edible resources (fish, crustaceans) in which metals bioaccumulate [START_REF] Ajani | Variability in levels of heavy metal in water and fish (Chrysichthys nigrodigitatus) tissues from Badagry creek, Nigeria[END_REF][START_REF] Somerset | Biomonitoring and evaluation of metal concentrations in sediment and crab samples from the North-West Province of South Africa[END_REF]Gbogbo et al., 2017). One of the difficulties for extended data collection is the lack of the laboratory infrastructure necessary to support the extensive monitoring of micropollutants over the African continent [START_REF] Madikizela | Status of pharmaceuticals in African water bodies: Occurrence, removal and analytical methods[END_REF][START_REF] Gwenzi | Organic contaminants in African aquatic systems: Current knowledge, health risks, and future research directions[END_REF]. (Gonzalez et al., 2014), and they have been recognized as potential micropollutants [START_REF] Pagano | Health effects and toxicity mechanisms of rare earth elements -Knowledge gaps and research prospects[END_REF]Hermann et al., 2016, Ebrahimi and[START_REF] Ebrahimi | Gadolinium as an emerging microcontaminant in water resources: threats and opportunities[END_REF].

Gadolinium (Gd) is certainly the most publicized REE, and large positive Gd anomalies (i.e., a concentration higher than that can be expected from the natural content in the crust) have been detected in Europe, Asia, Australia and America (Kulaksiz and Bau, 2011a;Merschel et al., 2015;Campos and Enzweiler 2016). The Gd concentration has also seemed to increase over time in Berlin (Germany) tap water [START_REF] Tepe | High-technology metals as emerging contaminants: Strong increase of anthropogenic gadolinium levels in tap water of Berlin, Germany, from 2009 to 2012[END_REF], in San Francisco Bay (California) [START_REF] Hatje | Increases in anthropogenic gadolinium anomalies and rare earth element concentrations in San Francisco Bay over a 20 year record[END_REF] or in the Garonne Estuary [START_REF] Lerat-Hardy | Rare Earth Element fluxes over 15 years into a major European Estuary (Garonne-Gironde, SWFrance): Hospital effluents as a source of increasing gadolinium anomalies[END_REF]. Positive Gd anomalies have been detected in two tributaries of the Hérault River (France) and in some wells supplying drinking water, corresponding to an excess of anthropogenic Gd in the water up to 15.4 pM (i.e.

2.4 ng/L) [START_REF] Rabiet | Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France)[END_REF]. Anomalies have also been detected for lanthanum (Kulaksiz andBau, 2011b, 2013;[START_REF] Klaver | Anthropogenic Rare Earth Element in rivers: Gadolinium and lanthanum. Partitioning between the dissolved and particulate phases in the Rhine River and spatial propagation through the Rhine-Meuse Delta (the Netherlands)[END_REF]Merschel and Bau, 2015;[START_REF] Shin | Anthropogenic rare earth elements and their spatial distributions in the Han River, South Korea[END_REF]Pignotti et al., 2017), samarium [START_REF] Kulaksiz | Anthropogenic dissolved and colloid/nanoparticle-bound samarium, lanthanum and gadolinium in the Rhine River and the impending destruction of the natural rare earth element distribution in rivers[END_REF]Merschel and Bau, 2015;[START_REF] Shin | Anthropogenic rare earth elements and their spatial distributions in the Han River, South Korea[END_REF] and cerium [START_REF] Hissler | Anthropogenic rare earth element fluxes into floodplains: Coupling between geochemical monitoring and hydrodynamic sediment transport modelling[END_REF]. Data from Africa are limited, but [START_REF] Ayedun | Evaluation of rare earth elements in groundwater of Lagos and Ogun States, Southwest Nigeria[END_REF] have reported than some REEs they found in Lagos State (Nigeria) could be related to leaching from wastes dumpsites. Similar to other metals, REEs accumulate in aquatic plants [START_REF] Chua | Bio-accumulation of environmental residues of rare earth elements in aquatic flora Eichhorniacrassipes (Mart) Solms in Guangdong Province of China[END_REF] and fish [START_REF] Mayfield | Examination of rare earth element concentration patterns in freshwater fish tissues[END_REF] and can impede the development of fish embryos and larvae [START_REF] Cui | Effects of rare earth elements La and Yb on the morphological and functional development of zebrafish embryos[END_REF][START_REF] Trifuoggi | Comparative toxicity of seven rare earth elements in sea urchin early life stages[END_REF]. Fears are emerging with regard to harmlessness of Gd to humans, particularly with the introduction of more stringent treatment of organic micropollutants in treatment plants, which may lead to a release of Gd from chelates used in medicine (Port el al., 2008). For REE other than Gd, concern has been recently raised in the vicinity of REE mining activities (Romero-Freire et al., 2018;[START_REF] Edahbi | Environmental challenges and identification of the knowledge gaps associated with REE mine wastes management[END_REF] with human health threatening conditions related to water resources and agricultural production [START_REF] Li | A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China[END_REF][START_REF] Hao | Evaluation of water quality in surface water and shallow groundwater: a case study of a rare earth mining area in southern Jiangxi Province, China[END_REF][START_REF] Liu | Water, sediment and agricultural soil contamination from an ion adsorption rare earth mining area[END_REF], prompting for more epidemiological surveys [START_REF] Huo | A pilot study on the association between rare earth elements in maternal hair and the risk of neural tube defects in north China[END_REF]Gwenzi et al., 2018).

In Benin, the access rates to sanitation are 17% and 61% in rural and urban areas, respectively (pS-Eau, 2018). A total of 70% of households discharge their wastewater in nature, and 20.1%

of households discharge their wastewater in courtyards [START_REF] Insae | Principal socio-demographic and economic indicators (Census of the population[END_REF]. In the case of Cotonou (Figure 1), the economic capital of Benin and the largest city in the country (680,000 inhabitants), most households (57%) dispose their wastewater in nature and 9.6% dispose their wastewater in courtyards. In addition, 7.2% and 3.5%

MATERIALS AND METHODS

Any data treatment was performed using Microsoft Excel.

Description of study area

Cotonou's watershed (6°20'N and 2°20'E) covers an area of 79 km 2 and extends 10 km to the west and 6 km to the east. The urban area, composed of 13 districts (INSAE, 2005), is bounded on the north by Lake Nokoué and on the south by the Atlantic Ocean. It is separated into two parts (western and eastern) by the Cotonou channel, which is the extension of Lake Nokoué towards the sea (Figure 1). The underground hydrological structure is complex, vertically as well as horizontally, with risk of saline water intrusions in the water table, originating from the ocean and Lake Nokoué [START_REF] Mcinnis | Combined application of electrical resistivity and shallow groundwater sampling to assess salinity in a shallow coastal aquifer in Benin, West Africa[END_REF]. The map was drawn using QGIS 3.6 (https://www.qgis.org) and is based on original data from SOGEFI (https://www.sogefi-sig.com).

According to the 4 th census of the population in 2013, the city has a population of 680,000 inhabitants. A total of 51% of the households in the city have access to drinking water provided by SONEB (Société Nationale des Eaux du Bénin) at home, and 46% visit other houses for this water. The water consumption is approximately 60 L/day/inhabitant. Some populations use this drinking water for all purposes, and others use it in addition to well water. The sewage system of Cotonou has a length of 306 km, with 30 subwatersheds in its western zone and 20 subwatersheds in its eastern zone.

Eastern zone

Segbeya 51 ha. Several drains connected to the main channel.

Midombo 36 ha. Similar characteristics as Segbeya.

The Vie-Nouvelle neighborhood, where the sampling of domestic wastewater was made over 24 hours, is a small housing complex of 50 villas and 316 apartments built as part of a low-income housing project initiated by the Benin Government in the 1970s. The apartments (approx. 1,200 inhabitants) are connected to a collection and treatment system for domestic wastewater (graywater and septic wastewater).

The only medical MRI scanner in Benin is in a private medical facility in Cotonou (Zongo-Nima district). It started to operate at the end of November 2016.

Sampling

The wastewater sampling campaigns were conducted by dry weather between October and December 2016. For each open sewer a composite sample was prepared by mixing equal parts of three grab sub-samples collected in the upstream, middle and downstream regions of the sewer. Figure 1 All samples were stored at 4°C and transported to the laboratory for analysis within 24 hours.

At all wastewater sampling sites, SONEB-delivered drinking water grab samples (1L at faucets) and well water grab samples (1L) were collected in April 2017. Soil samples were collected in five locations (Figures 1 and SI1 -Supplementary Information), dried in air for three days, sieved at 2 mm and ground.

Analyses

Wastewater sample turbidity was measured with a Wagtech (Thatcham, UK) turbidimeter. The chemical oxygen demand (COD) and ammonium of wastewater samples were analyzed according to the NF-T 90-101 and NF-T 90-015 (i.e., Nessler method) methods, respectively.

Filtration (0.45 µm pore size) was done prior to the ammonium determination. For the drinking water and well water samples, dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) were analyzed after filtration (0.45 µm pore size) on a VCHN (Shimadzu, Noisiel, France) by catalytic oxidation at 680°C and infrared detection of the produced carbon dioxide.

The NOx resulting from the oxidation was reacted with ozone, and the total dissolved nitrogen was finally quantified via luminescence. Calibration was done with potassium hydrogen phthalate for DOC and potassium nitrate for DTN.

The dissolved organic matter of the drinking water and well water samples was characterized optically. The UV-visible absorbance spectrum of each filtrated sample was measured between 200 and 700 nm using an Anthélie Light UV-visible spectrophotometer (Secomam, Alès, France) in a quartz cuvette (volume = 3.5 mL, optical path length = 1 cm). The blank was performed with ultra-pure water for solvent correction. Synchronous fluorescence spectra were obtained with a F-2500 fluorometer (Hitachi, Krefeld, Germany) equipped with a Xenon lamp, by using FL Solution 2.0 software. A fixed gap (50 nm) between the excitation and emission wavelengths (λex and λem, respectively) was used, with the excitation wavelength varying between 230 and 600 nm (wavelength step = 1 nm). The 50 nm gap was selected as a compromise to optimize the resolution of both the tryptophan-like fluorescence and the humiclike fluorescence [START_REF] Reynolds | Rapid and direct determination of tryptophan in water using synchronous fluorescence spectroscopy[END_REF]. A quartz cuvette was used (volume = 3.5 mL, optical path length = 1 cm). No correction for the inner-filter effect or the Rayleigh and Raman diffusion was performed, and the spectra were collected at the natural pH of the sample. The blank was performed with ultra-pure water. The fluorescence intensities were expressed in Raman units.

Deconvolution of the spectra was performed using the procedure developed by [START_REF] Assaad | Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)[END_REF], i.e., four fluorophores were extracted from the spectra: F1 (λexc = 280 nm, λem = 330 nm), F2 (λexc = 300 nm, λem = 350 nm), F3 (λexc = 320 nm, λem = 370 nm) and F4 (λexc = 355 nm, λem = 405 nm).

The REEs (lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and lutetium 10 (Lu)) were measured by inductively coupled plasma mass spectrometry (ICP-MS) in accordance with the NF EN ISO 17294-1 and NF EN ISO 17294-2 standards on a Thermo-Scientific ICAPQ ICP-MS. A natural river water certified reference material (SLRS-6 (NRC-CNRC)) was used to test the REE analytical procedure (Table 2). analyses were carried out on previously mineralized samples. For the digestion (40 min at 180°C under 9 bars in a microwave system equipped with PTFE vessels or tubes), 5 mL of ultra-pure nitric acid was added to liquid samples (20 mL) and to soil samples (0.15 mg, in triplicate). The final volume of the mineralized samples was 50 mL. Rhenium and rhodium were used as internal standards for soil analysis.

The Eu anomaly was calculated using Eq 1.:

= • ⁄
Eq. 1

where SmN and GdN are the normalized concentration in Sm and Gd, respectively. A ratio greater than 1 indicates a positive anomaly. The Eu anthropogenic excess was calculated using Eq. 2. [START_REF] Rabiet | Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France)[END_REF]:

Euanth = Eumeas-Eunat = Eumeas-(Eumeas /Euanom) Eq. 2
Unfortunately it was not possible to calculate anomalies related to Gd, due to the lack of Tb data.

RESULTS AND DISCUSSION

General characteristics of water and wastewater samples

The average pollution characteristics of the wastewater samples are given in Tables SI1 andSI2 (Supplementary Information Based on the 20 drinking water samples, the drinking water contained an average of 1.1 mgC/L (σ = 0.3 mgC/L) and 0.9 mgN/L (σ = 0.2 mgN/L), where σ is the standard deviation (Figure SI2). The drinking water synchronous fluorescence spectra revealed the presence of two fluorophores, F1 (protein-like fluorophore) and F4 (related to humic substances). It is likely that the presence of F1, indicative of biological activity, was due to biofilm development in the network.

The average concentrations of organic carbon and total nitrogen in the well water samples were 7 mgC/L and 18 mgN/L (with maximal values at 54 mg/L), respectively (Figure SI3). The organic carbon was mainly related to two fluorophores, F3 and F4, associated with humic substances (F3 and F4).

Fluorophore F1 was more present in the well water samples than in the drinking water. The presence of F1 could be due to biological activity in the wells, which were eventually polluted by untreated wastewater. The UV-visible spectra exhibited high absorbances in the UV range (<220 nm). There was a reasonable correlation (R 2 = 0.62) between the 225 nm maximum of the second derivation of the UVvisible spectra and the total dissolved nitrogen (Figure SI4). Based on the slope (486 (mgN/L)/(cm -1 nm - 2)), it is likely that most of the nitrogen is in the form of nitrates [START_REF] Pons | Nitrates monitoring by UV-vis spectral analysis[END_REF]. In such a case, 18 mgN /L corresponds to 80 mg NO3 -/L, much higher than values found by [START_REF] Toure | An investigation of some water quality properties from different sources in Pelengana commune, Segou, Mali[END_REF] in Mali (between 23 and 40 mg NO3 -/L depending upon the season), [START_REF] Wang | Characteristics, sources, water quality and health risk assessment of trace elements in river water and well water in the Chinese Loess Plateau[END_REF] in China (22 mg NO3 -/L in average but with a maximal value at 677 mg NO3 -/L) or Murray et al. (2018) in Maryland (< 4 mg NO3 -/L).

REE concentrations

Table 3 presents the concentrations of REEs in the wastewater samples of the different stations, as well as in both drinking water and well water. The values lower than the limit of quantification (LOQ) were not considered for the calculation of the average values. No effect of the MRI facility opening at the end of November 2016 could be detected, as all the Gd concentrations measured in December 2016 were lower than the LOQ (Table 4). Gd, Dy, Ho and Tm were mostly below the LOQ. The drinking water, which came from deep aquifers, had a total REE concentration (1.36 µg/L) higher than that of the well water samples (0.13 µg/L), which were pumped from the upper water table. All the REEs under consideration were detected in the drinking water at all sites.

For the well water samples, Gd, Dy and Tm were not detected in Ste Cécile, which was also true for the wastewater sampled in this neighborhood. Gd and Dy were not detected in Hinde, and Sm was not detected in Midombo. All the REEs were detected in the well water samples from Segbeya, Dantokpa, Jericho and Vie-Nouvelle. The REE concentrations in the drinking water and well water were much lower than those in the wastewater samples: based on Vie-Nouvelle wastewater, the ratios drinking water/wastewater varied between 30 (for Er) and 160 (for Ce) and the ratios well water/wastewater between 280 (for Er) and 620 (for Ce).

REE normalized profiles

The soil samples present REE profiles similar to those of NASC (North American Shales Composite) [START_REF] Bau | The European Shale: An improved data set for normalisation of rare earth element and yttrium concentrations in environmental and biological samples from Europe[END_REF] except for one sample (P5), which is slightly apart from the water sampling area (Figure 2). The REE soil concentrations were of the same order of magnitude as Lake Nokoué sediments, studied by [START_REF] Yessoufou | Rare earth and precious elements in the urban sewage sludge and lake surface sediments under anthropogenic influence in the Republic of Benin[END_REF]. Normalized REE (REEN) profiles were calculated, with NASC used as the reference (Figure 3). Deviations, such as enrichments of heavy REEs compared to light REEs and anomalies (deviation of an element compared to neighboring elements), can be detected in these profiles.

Anomalies are usually quantified by calculating the ratio between the normalized concentration of the element in the sample and the normalized concentration of that element in the case of no anomaly. The latter concentration is derived by averaging the normalized concentrations of the nearest neighbors of the deviating member [START_REF] Riou | Geochemistry Of Rare Earths And Associated Trace Elements In Groundwater And Water In Hydromorphic Soils[END_REF][START_REF] Olias | Temporal variations of REE in several AMD sources of the Odiel River (SW Spain)[END_REF]. However, in the present case, many REE exhibit wastewater concentrations lower than their LOQ and their anomalies were not calculated. Eu anomalies (Euanom (Eq. 1.) could be safely calculated for drinking water (1.31), well water (1.70) and wastewater samples from Segbeya (1.62), Hinde (0.91) and Vie-Nouvelle (1.28), using Sm and Gd concentrations.

The negative anomaly of Eu for the Hinde wastewater sample can be due to the high Gd concentration of this sample. This means that the measured Eu proportions in these samples were different from those of the reference system (i.e. NASC) [START_REF] Riou | Geochemistry Of Rare Earths And Associated Trace Elements In Groundwater And Water In Hydromorphic Soils[END_REF][START_REF] Rabiet | Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France)[END_REF]. Their presence could be due to the inorganic and organic ligands (e.g., F -, SO4 2-, CO3 2-, PO4 3-, fulvic and humic acids, proteins, and amino acids) in the environment that can complex more heavy REEs than light REEs [START_REF] Riou | Geochemistry Of Rare Earths And Associated Trace Elements In Groundwater And Water In Hydromorphic Soils[END_REF][START_REF] Rabiet | Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France)[END_REF]. According to [START_REF] Leleyter | REE distribution pattern in river sediments: partitioning into residual and labile fractions[END_REF], heavy REEs and cerium are preferably associated with iron oxides. In terms of of total iron an average of 2.4 mg/L for open sewers wastewater and 6.9 mg/l for domestic wastewater in Vie-Nouvelle were found, with the highest value found in Segbeya (7.7 mg/L). The Fe content can facilitate REE complexation and explain the HREE richness of these samples. The Vie-Nouvelle wastewater, which had the highest Fe concentration, had the greatest enrichment LaN/LuN, while the Dantokpa sample, which had the lowest Fe concentration (728 μg/L), had the lowest LaN/LuN (0.01).

The SONEB drinking water and well water samples had LaN/LuN of 0.56 and 0.25, respectively;

these values, which are less than 1, indicate an enrichment in HREE compared to LREE. REEs in natural waters come from the chemical alteration of soil minerals. With water, the main agent of this alteration consists of the partial or total dissolution of rocks or soils [START_REF] Riou | Geochemistry Of Rare Earths And Associated Trace Elements In Groundwater And Water In Hydromorphic Soils[END_REF]. This enrichment was observed in all sites. However, we note that the well water in Ste Cecile and Hinde presented an enrichment in LREE compared to HREE, with LaN/LuN ratios of 1.22 and 1.28, respectively. This situation could be due to particular conditions within these wells, which would merit further investigation. Wastewater samples from Segbeya and Vie-Nouvelle presented europium positive anomalies.

The anthropogenic excess calculated for these sites are 0.25 µg/L for Segbeya in sewer samples and 0.31 µg/L in the Vie-Nouvelle domestic wastewater. The SONEB drinking water and well water samples also showed europium anomalies of 1.31 and 1.70, respectively, but did not have an excess (0.00 µg/L). It can be deduced that the drinking water and well water were not sources of anthropogenic europium excesses in wastewater.

This europium excess in wastewater could come from another source, which could be related to the management of solid wastes in Cotonou. Some sources of europium are fluorescent lamps, television wastes, and smartphones [START_REF] Rollat | Prospective analysis of the flows of certain rare earths in Europe at the 2020 horizon[END_REF]. The runoff of leachates from waste piles in the streets to open sewers and to the sewage network of Vie-Nouvelle, as well as wastes themselves, which are thrown in abundance into the sewers, can explain this pollution; lead [START_REF] Youssao | Evaluation of the contamination of the ichthyan fauna in the Nokoué lagoon complex -Cotonou[END_REF] and cadmium [START_REF] Gbesso | Contamination of Tilapia guineensis by cadmium in Cotonou Channel[END_REF] pollution can be explained by this mismanagement of solid waste. Europium had a positive, significant correlation with turbidity (R 2 = 0.5) and could be adsorbed to the suspended matter, as the heavy metals (Cr, Cu, Ni, Pb and Zn) found in abundance in the wastewater and sewers samples.

SONEB water also showed a negative cerium anomaly (0.27). This anomaly is often observed in continental and marine water samples [START_REF] Riou | Geochemistry Of Rare Earths And Associated Trace Elements In Groundwater And Water In Hydromorphic Soils[END_REF][START_REF] Loges | Negative Ce anomalies in Mn oxides: The role of Ce4 + mobility during water-mineral interaction[END_REF]2012;[START_REF] Göb | Major and trace element compositions (including REE) of mineral, thermal, mine and surface waters in SW Germany and implications for water-rock interaction[END_REF][START_REF] Bau | The European Shale: An improved data set for normalisation of rare earth element and yttrium concentrations in environmental and biological samples from Europe[END_REF] and has been linked to the nature of the rocks.

CONCLUSION

Cotonou wastewater was affected by the presence of REEs, with an enrichment in heavy REEs In Benin and other African countries, the development of proper sanitation and solid waste management should help limit the dissemination of these ecotoxic substances in the aquatic environment and the food chain.

ACKNOWLEDGEMENTS

Figure 1 :

 1 Figure 1: Location of wastewater and drinking water sampling points in the city of Cotonou.

  shows the three sampling points on each open sewer. The sub-samples were collected in one-liter polyethylene bottles, with a sampler consisting of a jar attached to a rope. The sewer sampling campaigns were repeated six times between October and December 2016 (Oct 18, Oct 31, Nov 14, Nov 25, Dec 18, Dec 22). At Vie-Nouvelle, a 24 h sampling campaign (one 1L sample per hour) was conducted at the inlet of the wastewater treatment plant with an automatic sampler (Avalanche, Isco, Lincoln, NE, USA) in October 2016. A time-based composite sample was made for this sampling site.

Figure 2 :

 2 Figure 2: Cotonou soil REE profiles compared to NASC

  compared to light REEs. The two main REE were gadolinium and europium. The pollution by anthropogenic Gd is due to the use of Gd chelates as contrast agents for MRI. Gd contamination is likely to increase in the next few years with the improved access to MRI facilities and the absence of wastewater treatment plants. The europium pollution could be related to the mismanagement of solid wastes, whose leachates were found in sewerage networks. The aquifers are not yet polluted by Gd and Eu.

  Rare earth elements (REEs) represent a specific group of 15 metals ranging from lanthanum to lutetium. They are generally subdivided into two groups, light REEs (LREEs, from La to Eu) and heavy REEs (HREEs, from Gd to Lu). The REE signature in pristine waters is partially

inherited from rocks and sediments. REEs are increasingly used in high-tech devices (e.g., liquid crystal displays, communication devices, and solar panels) and to manufacture contrast agents for medical use, electric motors, batteries, catalysts, magnets, lamp triphosphors, phosphorescent paints, and other items. The concentrations of REEs have increased in the hydrosphere and in tap water

Table 1 :

 1 Characteristics of open sewers and subwatersheds of Cotonou Located in the central part of the city between the Aïdjèdo, Gbégamey, Fignon and Dantokpa districts. The road network is almost completely asphalted or paved, and the density of the secondary and tertiary drains is very important.

	Sewers

Table 1 presents the characteristics of the open sewers where sampling was conducted (MUHA, PUGEMU and IGIP AFRIQUE, 2014). Dantokpa 102 ha. Located in the city center. The main channel crosses the market area; the watershed is almost impermeable due to the very high rate of urbanization and the road surface. S te Cécile 269 ha. The watershed is largely impermeable due to the high rate of urbanization and the presence of paved or tarred roads.

Table 2 :

 2 Test of the SLRS-6 reference material Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES with argon plasma) (Thermo Instruments, Courtaboeuf, France). A quality control was run every ten samples. The metal and REE

		Reference value	% Error
		(ng/L) (Yeghicheyan
		et al., 2019)
	La	248.3	0.86
	Ce	292.7	0.05
	Pr	59.1	0.55
	Nd	227.8	1.15
	Sm	39.5	1.86
	Eu	7.26	7.07
	Gd	31.6	2.37
	Tb	4.07	16.13
	Dy	21.9	3.97
	Ho	4.3	6.13
	Er	12.4	5.46
	Tm	1.79	0.79
	Yb	11.2	2.39
	Lu	1.91	2.72

  As the samples were collected during dry weather, dilution by rain water in the open sewers is unlikely. However, infiltration from the water table can be expected due to its low depth and the deterioration of the open sewers: this can explain the low pollution concentration in the open sewers.

	Al and Fe were the metals with the highest concentrations in Vie-Nouvelle (6 mg/L and 7 mg/L,
	respectively), but in the open sewers, the concentrations of Mn (300 µg/L ±200 µg/L) could be higher
	than those of Al (360 µg/L ± 280 µg/L). In terms of heavy metals, Cu and Zn are expected to be present
	in significant concentrations (up to 908 µgCu/L and 224 µgZn/L in Vie-Nouvelle), but Cr, Ni and Pb
	are present in high concentrations in some samples: up to 40 µg Cr/L and 36 µg Ni/L in Vie-Nouvelle

). The COD and ammonium concentrations in open sewers were relatively low when the Vie-Nouvelle exhibited a very high COD concentration: the high pollution concentration in Vie-Nouvelle can be related to a low consumption of water in the housing complex. and 118 µg Pb/L in Hinde. However these values do not exceed the limits set by the Beninese legislation

[START_REF] Mehu | Decree N ° 2001-109 of 4 April 2001 setting the quality standards for wastewater in the Republic of Benin[END_REF]

.

[START_REF] Adjahouinou | Concentrations of heavy metals in raw wastewaters of Cotonou city (Benin)[END_REF]

found slightly higher concentrations in Cu, Pb, Zn, and Cd in wastewater samples collected in the same neighborhoods.

Table 3 :

 3 REE concentrations (µg/L): LOQ = Limit of quantification; min : minimum ; max = maximum ; aver = average ; ∑ REE = sum of REE

	249
			La	Ce	Nd	Sm	Eu	Gd	Dy	Ho	Er	Tm	∑ REE
	LOQ		0.0016	0.002	0.002	0.001	0.0002	0.0005	0.0003	0.0002	0.0003	0.0001
		min	0.002	0.1	1.1	0.6	0.3	<LOQ	<LOQ	0.01	0.5	<LOQ
	Ste Cécile	max	3.0	2.0	6.0	1.8	0.3	<LOQ	<LOQ	0.01	1.8	<LOQ	7
		aver	1.0	1.3	2.3	1.0	0.3	<LOQ	<LOQ	0.01	1.1	<LOQ
		min	0.6	1.9	2.2	1.0	0.3	7.3	5.2	0.05	0.7	<LOQ
	Hinde	max	17.6	12.9	29.7	7.6	1.8	7.3	5.2	1.0	3.9	<LOQ	34
		aver	4.1	4.9	7.4	2.3	0.8	7.3	5.2	0.4	1.7	<LOQ
		min	0.8	2.7	1.8	0.7	0.4	2.6	1.7	0.1	0.6	<LOQ
	Midombo	max	7.7	10.1	13.5	3.9	06	2.6	1.7	0.4	2.2	<LOQ	21
		aver	3.0	5.7	4.4	1.5	0.5	2.6	1.7	0.2	1.3	<LOQ
		min	2.6	3.4	0.3	1.1	0.4	1.8	<LOQ	0.07	0.42	<LOQ
	Segbeya	max	7.6	10.2	12.8	3.2	1.3	1.8	<LOQ	0.22	2.00	<LOQ	21
		aver	4.2	5.8	4.8	1.7	0.6	1.8	<LOQ	0.13	1.33	<LOQ
		min	0.1	0.7	0.3	0.4	0.3	<LOQ	<LOQ	0.03	0.4	<LOQ
	Dantokpa	max	1.3	14.6	4.3	1.5	0.3	<LOQ	<LOQ	0.04	1.9	<LOQ	10
		aver	0.9	4.6	1.9	0.9	0.3	<LOQ	<LOQ	0.04	1.1	<LOQ
		min	0.3	0.5	0.3	0.4	0.3	<LOQ	<LOQ	0.03	0.6	<LOQ
	Jericho	max	2.0	5.6	4.5	1.6	0.3	<LOQ	<LOQ	0.05	1.9	<LOQ	8.5
		aver	1.2	2.4	2.3	1.0	0.3	<LOQ	<LOQ	0.04	1.2	<LOQ
		min	0.3	1.9	1.6	0.7	0.02	0.00	0.05	0.00	0.6	0.00
	Cité Vie-Nouvelle	max	102.2	279.3	153.3	44.5	14.3	48.7	39.1	7.8	21.9	2.3	81
		aver	12.1	31.1	18.3	5.1	1.4	4.9	4.4	0.8	2.8	0.4
		min	0.02	0.003	0.03	0.01	0.003	0.01	0.01	0.003	0.01	0.001
	Drinking water	max	1.1	0.7	1.4	0.3	0.1	0.4	0.4	0.1	0.3	0.0	1.37
		aver	0.3	0.2	0.4	0.1	0.03	0.1	0.1	0.03	0.1	0.01
		min	<LOQ	0.001	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ
	Well water	max	0.1	0.2	0.1	0.02	0.01	0.03	0.02	0.01	0.02	0.003	0.15
		aver	0.02	0.05	0.03	0.01	0.003	0.01	0.01	0.002	0.01	0.001

Table 4 :

 4 Gd concentrations in the open sewers inOct-Nov 2016 (prior to MRI opening) and Dec 2016 (after MRI opening). Vie-Nouvelle WWTP). Concerning the sewers, Hinde was the site with the highest REE concentration (35 μg/L). Holmium was the REE with the lowest concentrations in all sites.Thulium was not detected in any sewer, but it was detected in Vie-Nouvelle. Neodymium was the REE with the largest concentrations in Ste Cécile, Hinde, Midombo and Segbeya. Cerium was the REE with the largest concentrations in Dantokpa, Jericho and Vie-Nouvelle WWTP.

		Ste-Cécile	Hinde	Midombo	Segbeya	Danktopa Jericho
	Oct-Nov	<LOQ	7.3	2.6	1.8	<LOQ	<LOQ
	2016
	Dec 2016	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ
	The REE total concentration in the wastewater samples varied from 8 µg/L (Ste Cécile) to 82
	µg/L (

  Although it was not possible to calculate Gd anomalies, challenging Gd values were observed in Hinde, Midombo, Segbeya open sewer samples and Vie-Nouvelle wastewater samples. They are much larger than the Gd concentrations of the drinking water and well water samples collected in the area. The highest concentration is detected in Vie-Nouvelle wastewater samples (up to 48.7 µg/L) when the drinking water highest concentration is 0.4 µg/L. It is likely that these high Gd values can be attributed to the presence of gadopentetic acid or other Gd salts used in medical MRIs. The Gd compounds, which are injected in a complex form into patients during examinations, are subsequently completely excreted by the patients and thereby contaminate wastewaters. The content of anthropogenic Gd is random because it depends on the number of people undergoing MRI examinations. Gadolinium had a significant correlation with COD (R 2 = 0.9) and no correlation with turbidity. It also had a significant correlation with ammonium (human pollution indicator) (R 2 = 0.9). This confirms that the gadolinium came from human pollution, in spite of the quasi-absence of MRI facilities in Benin. The only facility opened in November 2016 and was likely not fully operational at the time of the wastewater samplings. However, such facilities are available in neighboring countries (Togo, etc.); it is possible that patients traveled abroad for MRI examinations and returned home with Gd still in their bodies. Unfortunately, there are very few data in literature regarding the content of REE in untreated wastewater. In[START_REF] Verplanck | Aqueous stability of Gadolinium in surface waters receiving sewage treatment plant effluent, Boulder Creek, Colorado[END_REF] normalized Gd concentrations in primary influents of large WWTPs in USA of about 5⋅10 -4 are given, but the water consumption is very different: between 200 and 700 L/day/person in USA, when in Cotonou it is about 60L/day/person. So the comparison is difficult.

Channel by lead: case of the species Sarotherodon melanotheron, Tilapia guineensis and Hemichromis fasciatus (Benin). IJBCS, 5, 595-602.


Aust Stefanie1

Eberst Lauriane2

Tredan Olivier2

Rousset-Jablonski Christine

Treilleux Isabelle2

Méeus Pierre3

Chopin Nicolas3

Beurrier Fred3

Charreton Amandine2

Véronique Daval2

Hallouz Amina2

Coulon Agnès2

Ricoeur Alexis4

Mastier Charles4

Bouhamama Amine4

Racadot Séverine5

Devouassoux-Shisheboran Mojgan6

Haddad Véronique2

Ray-Coquard Isabelle7
email: isabelle.ray-coquard@lyon.unicancer.fr

Detailed overview on rare malignant ovarian tumors Les tumeurs rares de l'ovaire

Keywords: germ cell tumors, sex cords stromal tumors, mucinous carcinoma, clear cell carcinoma Résumé

The group of rare malignant ovarian tumors includes the group of germ cell tumors, sex cords stromal ovarian tumors, small cell carcinoma, malignant Brenner tumors, rare epithelial tumors such as mucinous carcinoma, clear cell carcinoma, or low-grade serous carcinoma, as well as ovarian carcinosarcoma. Together they comprise about 10% of all ovarian tumors. Due to their low prevalence and their heterogeneity, data and treatment recommendations are limited. Even though all ovarian tumors are staged according to the FIGO staging of epithelial ovarian tumors, treatment differs especially in germ cell tumors and sex cords stromal ovarian tumors. Non-epithelial ovarian tumors can arise from a variety of ovarian precursor cells such as germ cells, granulosa cells, theca cells, or stromal fibroblasts. As can be expected already due to their divergent precursor lesions, these malignancies are substantially different but united by their rarity. This overview article gives a comprehensive summary on the pathology and clinical presentation, as well as therapy recommendations of a selection of those rare ovarian tumors, based on the latest national guidelines and related important publications.

Rare ovarian tumors

A tumor is defined as rare, if an incidence of less than six per 100 000 per year is documented in the respective population. Due to their rarity, diagnose might be difficult and a histological review by an expert pathologist is recommended, including a comprehensive molecular characterization to guide further treatment. Outcome significantly improves if rare tumors are treated in a referral center [START_REF] Ray-Coquard | Improving treatment results with reference centres for rare cancers: where do we stand?[END_REF]. To provide a national-wide access to dedicated experts in the field of rare ovarian tumors and to improve the clinical management of those rare malignancies, a comprehensive website (www.ovairerare.org) and associated network was developed in France in 2004. Due to its constantly growing activity, the national network for rare ovarian/gynecological cancers (TMRG) was officially labeled in 2011, comprising a 3-site national expert center and 22 regional reference centers. The website "www.ovaire-rare.org" enables clinicians an easy access to accurate treatment recommendations with regular updates. Additionally, clinicians can discuss patient management by integrating them in a regional referral multidisciplinary tumor board specialized on rare ovarian tumors. This expertbased tumor board is held in a weekly basis and also provides a structure to facilitate the organization of a respective histological review by a listed pathological expert. Recommendations are based on therapy guidelines publicly available on the website and additionally allow the proposition of clinical trials to enable access to targeted therapies if applicable. Creating a national network with a dedicated system for referral, the management of rare ovarian tumors can be monitored and an equal national-wide access to medical expertise provided [START_REF] Chiannilkulchai | Networking for ovarian rare tumors: a significant breakthrough improving disease management[END_REF][START_REF] Ray-Coquard | Rare ovarian tumours: therapeutic strategies in 2010, national website observatory for rare ovarian cancers and delineation of referent centers in France][END_REF]. This article will present an overview on malignant germ cell tumors, sex cords stromal ovarian tumors, rare epithelial tumors such as mucinous carcinoma and clear cell carcinoma but also ovarian metastases of non-ovarian origin as they need to be considered in differential diagnosis. A detailed decision-path for each tumor entity can be accessed at www.ovaire-rare.org [4].

Germ cell tumors

Malignant germ cell tumors (GCT) are diagnosed in approximately 5% of all malignant ovarian tumors. They are distinguished from epithelial ovarian cancers by several factors such as diagnosis in younger women, often rapid tumor growth and thus respective related symptoms leading to a diagnosis in early stages and a significantly better prognosis, as well as a different set of relevant biomarkers (serum human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP), and lactate dehydrogenase (LDH) [START_REF] Brown | Gynecologic Cancer Intergroup (GCIG) consensus review for ovarian germ cell tumors[END_REF]). It has to be noted, that malignant GCTs represent 80% of the preadolescent malignant ovarian tumors. Thereof, dysgerminoma, immature teratoma, and yolk sac tumor are the most important representatives. The complete list of GCTs is depicted in Table 1 and the detailed respective treatment recommendations can be downloaded from www.ovaire-rare.org [6].

Dysgerminomas are the most common malignant GCTs and can be seen as the equivalent to male testicular seminoma. Incidence is highest in the second and third decade. Bilateral tumors can occur in up to 15% [START_REF] Gershenson | Malignant germ-cell tumors of the ovary[END_REF]. Elevated serum LDH is characteristic; rarely elevation of serum b-HCG and AFP can also be present. The immunohistochemical profile of those large solid tumors comprises CD117 (strong, membranous expression in approximately 80% of cases), SALLA-4 (diffuse, nuclear expression), OCT3/4 (nuclear expression), and D2-40 (membranous and cytoplasmic expression) [START_REF] Euscher | Germ Cell Tumors of the Female Genital Tract[END_REF].

In young dysgerminoma patients presenting with primary amenorrhea, an XY gonadal dysgenesis has to be excluded by chromosomal analysis as subsequently, the confirmation of an XY gonadal dysgenesis would lead to a bilateral adnexectomy.

Malignant Teratoma: Immature Teratomas only represent about 1% of all teratomas and contain immature cells derived from the three germ-cell layers (ecto-, endo-, and mesoderm as well as immature neural elements) [START_REF] Gershenson | Malignant germ-cell tumors of the ovary[END_REF][START_REF] Kurman | Malignant germ cell tumors of the ovary[END_REF]. Immature teratomas are usually unilateral, lobulated tumors with hemorrhagic and necrotic areas. Microscopically, a variety of cells representing those three germ-cell layers can be identified in different stages of differentiation. The grade is determined by the respective amount of immature neuroepithelium.

Most patients with early-stage immature teratoma are managed with fertility sparing surgery (whereby the respective surgical staging criteria have to be fulfilled), chemotherapy, and close follow up and have an excellent prognosis [START_REF] Jorge | Characteristics, treatment and outcomes of women with immature ovarian teratoma, 1998-2012[END_REF].

Yolk sac tumors (endodermal sinus tumors) are rapidly growing, aggressive tumors usually diagnosed in younger women and characterized by elevated serum AFP levels. Microscopically, they comprise a multiplicity of histological patterns and diagnosis can be difficult. Immunohistochemically, the expression of SALLA4 (a marker of primitive germ cell differentiation) as well as AFP or Glypican 3 is observed (SOX2 and OCT3/4 negative). In contrast to other GCTs, the standard treatment comprises adjuvant chemotherapy after surgery even in stage I disease [START_REF] Ray-Coquard | Non-epithelial ovarian cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up[END_REF]. Although in selected optimally staged (pediatric) patients with stage I disease and negative post-operative AFP levels, surveillance might be considered [START_REF] Billmire | Surveillance after initial surgery for pediatric and adolescent girls with stage I ovarian germ cell tumors: report from the Children's Oncology Group[END_REF].

Taking into account that the majority of patients with GCTs are diagnosed in stage I and at a young age with excellent long-term survival results, fertility preservation is of high importance. Fertility sparing unilateral salpingo-oophorectomy is thus generally recommended and can be considered even in advanced stages in pre-menopausal women because of the high chemotherapy sensitivity of GCTs. In women of childbearing age, specific information on infertility risks and on fertility preservation options should be implemented [START_REF] Rousset-Jablonski | Fertility preservation, contraception and menopause hormone therapy in women treated for rare ovarian tumours: guidelines from the French national network dedicated to rare gynaecological cancers[END_REF]. The initial surgery has the aim to determine the exact tumor stage by comprehensive exploration of the abdominal cavity, followed by a complete surgical staging after cytology has been taken. Systematic biopsy of the contralateral ovary is not recommended, neither systematic lymphadenectomy. Given the high chemotherapy-sensitivity, nodal metastases should be cured by adjuvant treatment. But even in stage I disease where no adjuvant chemotherapy is planned, lymphadenectomy only needs to be performed if bulky nodes are present during surgery or on pre-operative imaging.

Malignant germ cell tumors of the ovary are highly sensitive to cisplatin-containing combination chemotherapies. The therapy of choice represents the combination chemotherapy with bleomycin, etoposide and cisplatin (BEP scheme). In principle, the majority of patients with malignant GCTs in stages >=2 will receive chemotherapy whereby the number of cycles depends on specific criteria (e.g. complete surgical resection and tumor marker levels post-surgery). In stage I disease the option of an adjuvant chemotherapy should be discussed with the patient in grade 2 and 3 as well as all IB/IC immature teratoma, stage IC dysgerminoma if an adequate surveillance can't be guaranteed, and in all stage I yolk sac tumors (besides rare cases of stage IA disease with adequate AFP and LDH levels after surgery if an active and intensified surveillance will be performed) [6,[START_REF] Gershenson | Current advances in the management of malignant germ cell and sex cordstromal tumors of the ovary[END_REF].

The BEP scheme has not negligible adverse effects (of importance the pulmonary toxicity for bleomycine) and an associated risk of consecutive second malignancies. An international clinical trial (AGCT1531; ClinicalTrials.gov identifier: NCT03067181) is thus currently evaluation the outcome of surgery alone followed by BEP chemotherapy at time of tumor recurrence patients with stage I grade 2, 3 ovarian immature teratoma and all low-risk stage I malignant germ cell tumors [15].

Early stage, young age (<45years), low grade and complete staging surgery are positive prognostic factors [START_REF] Mangili | Outcome and risk factors for recurrence in malignant ovarian germ cell tumors: a MITO-9 retrospective study[END_REF]. Adequate therapy of malignant germ cell tumors leads to an excellent overall survival, especially in stage I disease. In advanced stages after completing adjuvant chemotherapy treatment, failure is nevertheless observed in about 25% of patients [START_REF] Gershenson | Current advances in the management of malignant germ cell and sex cordstromal tumors of the ovary[END_REF]. More than two third of recurrences are diagnosed already within the first year after initial management. Recurrence occurs mainly locally in the peritoneal cavity.

A rare particularity in patients that had been treated for immature teratoma is the development of a benign "growing teratoma syndrome". As recurrence is not common, alternative benign diagnoses should be considered in the case of progressing intra-abdominal masses without associated elevated tumor markers. In this context, histological findings comprise benign mature teratoma, sometimes associated with peritoneal gliomatosis [START_REF] Merard | Growing Teratoma Syndrome: A Report of 2 Cases and Review of the Literature[END_REF]. In complementary imaging, mature elements such as fat or areas of calcification might be present within those masses. The growing teratoma syndrome has first been described in male patients after treatment of nonseminomatous germ cell tumor [START_REF] Logothetis | The growing teratoma syndrome[END_REF] and occurs seldom in women. Due to its rarity, a growing teratoma could thus easily be misinterpreted as disease progression or recurrence. Chemotherapy and radiation are not effective and only cause side effects; a reasonable, surgery-based treatment and observation thus has to be implemented [START_REF] Bentivegna | Surgical Outcomes After Debulking Surgery for Intraabdominal Ovarian Growing Teratoma Syndrome: Analysis of 38 Cases[END_REF].

Sex cords stromal ovarian tumors (SCSTs)

Tumors of the stromal (Leydig cells) and/or sex cords (Granulosa or Sertoli cells) as depicted in Table 2 represent approximately 7% of ovarian neoplasms and develop from the stromal tissue that surrounds the oocytes (interstitial and nurse cells). Tumors arising from a sex cord component such as granulosa or Sertoli cells are rare and diagnosed in about 5% of malignant ovarian tumors [START_REF] Stewart | An immunohistochemical and molecular analysis of problematic and unclassified ovarian sex cord-stromal tumors[END_REF]. An important difference to germ cell tumors is the fact that SCSTs have no particular age dependency and that they are diagnosed in all age groups. Nevertheless, the mean age at the time of diagnosis is lower than in epithelial ovarian cancer. In addition, they are essentially more often endocrine active (in about 66% of cases) and occur usually unilateral. The most common representative of malignant SCSTs are granulosa cell tumors. Sertoli-Leydig cell tumors, steroid cell tumors, gynandroblastoma and SCST with annular tubules are extremely rare.

Granulosa cell tumors are typically large unilateral adnexal masses with heterogeneous solid, cystic, as well as hemorrhagic components. Granulosa cell tumors are often endocrine active and lead to increased estrogen production that may result in various clinical symptoms such as a hyperplastic or malignant transformation of the endometrium or in young women the appearance of a pseudoprecocious puberty.

Two forms of granulosa cell tumors are to be distinguished: the juvenile type and the adult type, whereby the later accounts for 95% of all granulosa cell tumors. Tumors of the adult type are characterized by a slow progression and occurrence of late recurrences, surveillance thus has to be adequate. FOXL2 mutation is virtually present in almost all granulosa cell tumors of the adult type and the determination of FOXL2 (402C→G) mutation distinguishes this type from other SCSTs [START_REF] Shah | Mutation of FOXL2 in granulosa-cell tumors of the ovary[END_REF]. Immunostaining for FOXL2 on the other hand is present in the majority of SCSTs and thus together with α-inhibin and calretinin a general marker for SCSTs [START_REF] Huwait | FOXL2 is a sensitive and specific marker for sex cordstromal tumors of the ovary[END_REF].

On the other hand, the juvenile type account for only about 5% of all granulosa cell tumors and is typically found before puberty -especially in the first life decade. Tumor recurrences are rare as tumors are usually diagnosed in early stage with good prognosis. In advanced stages relapse is frequently observed and associated with poor outcome [START_REF] Wu | Juvenile Granulosa Cell Tumor of the Ovary: A Clinicopathologic Study[END_REF].

As granulosa cells produce inhibin, serum levels rise with the growth of granulosa cell tumors. Inhibin B as well as AMH can thus be used as markers to monitor disease recurrence and progression in both, adult and juvenile type.

Fertility sparing surgery is the standard treatment for granulosa cell tumors of the juvenile type. These tumors are usually confined to one ovary and recurrence is seldom observed after simple unilateral salpingo-oophorectomy. In the rare cases of advanced stage or tumor recurrence, chemotherapy needs to be considered. Platinum-based chemotherapy is considered the therapy of choice [START_REF] Ray-Coquard | Non-epithelial ovarian cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up[END_REF]. Still, it has to be noted that data on adjuvant treatment regimens are limited. Surgery is likewise the cornerstone in treatment of tumors from the adult type. Debulking surgery remains the most effective treatment not only in early but also in advanced stage. Even in recurrence, debulking surgery should be considered whenever feasible [START_REF] Ray-Coquard | Gynecologic Cancer InterGroup (GCIG) consensus review for ovarian sex cord stromal tumors[END_REF]. An endometrial curettage needs to be performed in fertility sparing approaches to rule out concomitant endometrial pathologies. In advanced stage or recurrence, if not completely resected, adjuvant platinum-based therapy (either BEP or Carboplatin/Paclitaxel) is recommended. Hormonal anti-estrogen therapy seems to be a potential alternative in recurrent adult granulosa cell tumors.

Sertoli-Leydig cell tumors (SLCT) are usually diagnosed in young women as unilateral, early stage tumors. They comprise three grades according to the degree of differentiation of the Sertoli cell component of the tumor (well, intermediate and poorly differentiated tumors). Additionally, the presence of heterologous elements as well as a retiform pattern have a prognostic significance. Associated virilization signs are present in about 80% of patients due to an increased androgen production. Macroscopically, they appear as solid tumors with a smooth surface. Mutation in DICER1 occurs in a subset of SLCTs and might be prognostic relevance [START_REF] Goulvent | DICER1 and FOXL2 mutations in ovarian sex cordstromal tumours: a GINECO Group study[END_REF]. If a germline DICER1 mutation is diagnosed, subsequently screening of family members has to be considered.

Fertility sparing surgery is the standard treatment as the majority of tumors are diagnosed in early stage. A currently published analysis of The U.S National Cancer Data Base, including 286 patients with Sertoli-Leydig cell carcinoma, there was no difference in overall survival in patients receiving adjuvant chemotherapy (n=180) versus no adjuvant treatment (n=150) in stage I disease (5-year OS rates 85.1% and 85.7%, respectively) or stage II disease (n=25), correct surgery might thus be sufficient in early stage. In advanced stage, a significantly better OS was observed for patients treated with chemotherapy [START_REF] Nasioudis | Role of adjuvant chemotherapy in the management of non-granulosa cell ovarian sex cord-stromal tumors[END_REF]. As stage and grade are important prognostic parameters, adjuvant chemotherapy should be considered in tumors with poor differentiation or heterologous elements regardless of the FIGO stage [START_REF] Ray-Coquard | Non-epithelial ovarian cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up[END_REF].

Stromal tumors (such as fibromas, thecomas, and Leydig cell tumors) are usually benign, nevertheless they should be mentioned as they need to be considered as differential diagnosis.

Thereof, fibromas are the most common histological type. They usually occur unilateral in postmenopausal women and are not hormonally active. Thecomas are very rare and mostly benign. Likewise, they occur usually unilateral but can produce both, estrogen as well as androgensclinically related to varying endocrine symptoms. Leydig cell tumors are rare, usually unilateral but appear in contrast to the other germline stroma tumors in young women. In the majority of cases an increased androgen production is present but estrogen production can likewise be observed.

Rare malignant epithelial tumors

Rare ovarian carcinomas comprise low-grade serous, endometrioid, mucinous or clear cell carcinomas. We will further discuss the subgroups of mucinous and clear cell carcinomas. Compared to high grade serous epithelial ovarian cancer (HGSOC) they are more often diagnosed in earlier stage and considered to be less chemotherapy responsive. Additionally the classical epithelial marker CA-125 is not a reliable marker in non-HGSOC.

Mucinous ovarian carcinomas are of particular interest. The exact incidence of mucinous ovarian carcinomas is probably even lower than estimated as differential diagnosis from digestive metastatic tumors can be difficult and thus diagnose might not be accurate in all cases. Systematic realization of digestive endoscopies is at least required when the tumor is bilateral or less than 10 cm, or with peritoneal involvement. In low grade stage I disease, the differential diagnosis between invasive-and borderline tumors might likewise be difficult. In intra-operative frozen section analysis the determination of malignancy is complicated by the fact of different histologic components comprised in mucinous carcinomas, including benign cystadenoma as well as borderline aspects and intraepithelial carcinoma.

Contrary to HGSOC, mucinous ovarian carcinoma occurs in younger age and is often diagnosed in early stage. However, if diagnosed in an advanced stage prognosis is inferior to HGSOC and these cases a metastasis from gastrointestinal or pancreatic primary should be ruled out. On the molecular level, KRAS is mutated in over 40% and P53 mutation is rarely detected (20%).

The pathology report should include the sub-classification of a mucinous carcinoma according to their growth pattern into either an expansile or a destructive-invasive type. This approach was proposed in 2014 by the WHO as prognosis differs according to the respective morphologic differences. Thereof, the expansile type has the better prognosis and treatment needs thus to be adapted to the respective classification [START_REF] Lee | Mucinous tumors of the ovary: a clinicopathologic study of 196 borderline tumors (of intestinal type) and carcinomas, including an evaluation of 11 cases with 'pseudomyxoma peritonei[END_REF].

In total, a staging surgery should be considered, regardless of the sub-type. The role of systematic lymphadenectomy has been under discussion for long as generally literature was in favor of a rare incidence of lymph node metastases in mucinous ovarian carcinomas. Recently, a comprehensive analysis of mucinous ovarian carcinomas (stratified into the respective morphologic subtypes) showed that lymph node metastases are present in >10% (17%) of carcinomas of the invasive type. This might justify restaging surgery for lymph node-excision in this subtype for diagnostic implications but if a therapeutic benefit can be obtained remains still an open question [START_REF] Gouy | Staging surgery in early-stage ovarian mucinous tumors according to expansile and infiltrative types[END_REF]. Additionally the role of appendectomy (particularly related to the question of restaging surgery) needs to be questioned if the appendix is macroscopically normal appearing [START_REF] Lin | The role of appendectomy for mucinous ovarian neoplasms[END_REF].

Adjuvant treatment recommendations differ according to the histological subtype. For stage I tumors the indication of adjuvant treatment is under discussion and thus either observation, platinum-based Chemotherapy or a protocol derived from gastrointestinal tumors are proposed in literature. The 2019 ESMO guidelines recommend adjuvant chemotherapy in the infiltrative type already in stage I disease (thereof optional in IA) [START_REF] Colombo | ESMO-ESGO consensus conference recommendations on ovarian cancer: pathology and molecular biology, early and advanced stages, borderline tumours and recurrent diseasedagger[END_REF]. Platinum-based chemotherapy is recommended for all patients with stage II to IV disease. A detailed decision-path can be accessed at www.ovaire-rare.org [4]. Given the lower response rate to platinum-based chemotherapy in mucinous carcinoma compared to HGSOC, a gastrointestinal-type regimen can likewise be considered. Targeted treatments in tumors with KRAS mutation or HER2 amplification could be an interesting approach in mucinous carcinomas but given the rarity, performing clinical trials rests difficult [START_REF] Gershenson | Management of Rare Ovarian Cancer Histologies[END_REF][START_REF] Morice | Mucinous Ovarian Carcinoma[END_REF].

Similar to mucinous ovarian carcinoma, Clear cell carcinoma is often diagnosed in early stage. The incidence of this epithelial tumor differs according to the studied population, considered a rare ovarian tumor in Western countries (about 5% of ovarian carcinomas), occurrence is significantly higher in East-Asia (up to 27% of EOC in Japanese women) [START_REF] Sugiyama | Clinical characteristics of clear cell carcinoma of the ovary: a distinct histologic type with poor prognosis and resistance to platinum-based chemotherapy[END_REF]. Clear cell carcinoma may be associated with endometriosis or Lynch syndrome and has an interesting molecular profile. PIK3CA and ARID1A mutation co-occur frequently [START_REF] Kim | Genomic landscape of ovarian clear cell carcinoma via whole exome sequencing[END_REF]. Associated paraneoplastic symptoms such as hypercalcemia are another characteristic of this rare tumor. Despite diagnosed often in early stage, clear cell histology is a negative prognostic factor. Relapse is frequently observed already in stage IC disease (37%) [START_REF] Sugiyama | Clinical characteristics of clear cell carcinoma of the ovary: a distinct histologic type with poor prognosis and resistance to platinum-based chemotherapy[END_REF].

The basis of treatment is surgery, whereby the standard surgical approach of staging and debulking surgery is the same as in other EOCs. For rare epithelial carcinoma such as clear cell carcinoma, platin-based chemotherapy remains the standard treatment even though the efficiency observed in HGSOC is not reached. Certainly, drug-resistance to conventional chemotherapy is contributing to the poor prognosis of clear cell carcinoma [START_REF] Itamochi | Mechanisms of chemoresistance and poor prognosis in ovarian clear cell carcinoma[END_REF]. Several clinical trials are ongoing comparing different therapeutic approaches, such as targeting the PI3K/AKT/mTOR pathway, tyrosine kinase inhibitors or immunotherapy to determine alternative therapeutic approaches in this aggressive and commonly platin-resistant tumor. Although the benefit of platin-based chemotherapy remains uncertain, adjuvant treatment is to be discussed and evaluated individually even in stage I disease (thereof optional in stages IA, IB and ICI) [START_REF] Colombo | ESMO-ESGO consensus conference recommendations on ovarian cancer: pathology and molecular biology, early and advanced stages, borderline tumours and recurrent diseasedagger[END_REF].

Ovarian metastases from non-ovarian origin

The primary site of disease has an important impact on prognosis and treatment of cancer. Thus, it needs to be considered that a small number of ovarian malignancies are metastases of primary tumors with non-ovarian origin. These include metastases from gastro-intestinal carcinomas (stomach, colon, and appendix), but also breast cancer, or rarely pancreatic, gallbladder or urinary bladder cancer [START_REF] Kiyokawa | Krukenberg tumors of the ovary: a clinicopathologic analysis of 120 cases with emphasis on their variable pathologic manifestations[END_REF]. Gastric cancer probably accounts for the predominant primary tumor with ovarian metastases, accounting for an increased incidence of so called Krukenberg tumors in Asian women. These tumors often occur bilateral, consistent with a metastatic origin, and are normally limited to the ovaries. As previously discussed, mucinous ovarian carcinomas can be difficult to distinguish immunohistochemically from ovarian metastases of tumors harboring a gastrointestinal origin -thus especially in bilateral tumors a comprehensive clinical gastro-intestinal evaluation has to be performed. Surgical and (neo) adjuvant treatment relies on the guidelines of the respective primary tumor.

tumeurs des cordons sexuels et du stroma, le carcinome à petits cellules, la tumeur de Brenner maligne, des tumeurs épithéliales rares telles que le carcinome à cellules claires, le carcinome mucineux, et le carcinome séreux de bas grade, et également le carcinosarcome ovarien. Au total, elles représentent environ 10% de l'ensemble des tumeurs ovariennes. En raison de leur faible prévalence et de leur hétérogénéité, les données et les recommandations de traitement sont limitées. Bien que toutes les tumeurs ovariennes soient classées selon la classification FIGO des tumeurs épithéliales de l'ovaire, le traitement diffère en particulier dans les tumeurs germinales et les tumeurs de l'ovaire des cordons sexuels et du stroma. Les tumeurs ovariennes non épithéliales peuvent provenir d'une variété de cellules précurseurs de l'ovaire telles que des cellules germinales, des cellules de la granulosa, des cellules thécales ou des fibroblastes stromaux. Comme on peut s'y attendre déjà en raison de la diversité de leurs lésions précurseurs, ces tumeurs malignes sont substantiellement différentes -mais unies par leur rareté. Cet article donne un résumé complet de l'histopathologie et de la présentation clinique, ainsi que des recommandations thérapeutiques de certaines de ces tumeurs rares de l'ovaire, sur la base des dernières recommandations nationales et des publications importantes.Mots-clés: tumeurs germinales, tumeurs des cordons sexuels et du stroma, carcinome mucineux, carcinome à cellules claires

Beyond standard treatment

Patients with rare tumors need an adequate treatment. Respective therapy recommendations can only improve if clinicians work together, national-wide and internationally. Integrating rare tumor cases in respective networks and organizations (e.g. the European Reference Networks on rare cancers EURACAN) not only enhances our general understanding of those diseases but also enables the conduction of clinical trials and the future development of new treatment strategies.

Conflict of interest none