In this study, we have first addressed the main demographic and clinical characteristics of breast cancer in a cohort of patient women referred to the CNO (Centre National d’Oncology) and assessed the outcome of cancer in the context of these factors. Out of 11175 patient files of all cancer types, BC was the most common in the cohort population (16.56%), particularly in women (30.9%). This standing was also reported by a ten years study (from 2000 to 2009) which included 3305 histological samples analyzed by the department of anatomic pathology (Hopital National de Nouakchott) and showed a prevalence of 14.6% in the whole cohort and 25.2% among the female population.As our study was conducted in the following decade of the previous work and covered the single state referring facility for cancer, the data generated were therefore likely representative of the disease evolution in the country. Their concordance reflected an increase in the incidence of breast cancer in our population. Similar percentages of breast cancer in women were reported in neighboring populations such as in Morocco(36%)[8, 11]and Senegal (26.1 %) .
Most women diagnosed with breast cancer (69%) in our study were ages55 or less.Registriesand community-based studies showed that 70% of women with breast cancer in Sub-Saharan Africa were in the same age group .The mean age of 49 years we observed was thus close to the 48 years reported globally in Africa and 46 years in British black women.This relatively early onset of breast cancer was lower than late age of 67 years at presentation in white British women . Pre-menopausal status was also predominant in our cohort (63 %) as in two-thirds of black African women with BC [16–17] while most of Europeanwomen (80 %) were postmenopausal at presentation with the disease .
We also observed that most patients (66%)hadmoderate to poorly differentiated tumors with widely spread stage 3 (44%) or metastasized (22%) cancer when diagnosed with BC. A similar outline was reported in a 12 sub-saharan countries study (Zimbabwe, Benin, Seychelles, Ethiopia, Mauritius, South Africa, Kenya, Mozambique, Mali, Namibia, Uganda and Cote d'Ivoire)showing that 64.9% of women patients were diagnosed in late stages, when treatment became weakly effective, of which 18.4% being metastatic at diagnosis .This late advanced stage at presentation, very likely accentuated by poor socioeconomic conditions and lack of access to adequate healthcare, could be therefore determinant in the low 2- and 3‐year observed survival rate of 74% and 64% observed in our cohort and the overall relative survival (RS) of 61.4% (59.1–63.5) at year 3 and 52.3% (49.9–54.6) at year 5in BC patients across sub-Saharan Africa. In contrast, 79% and 89% of women with breast cancer respectively in Europe and the US had not died from their cancer 5 years later after diagnosis .
Despite evidences reported from many large cohort studies linking overweight to breast cancer risk[21–22], nearly 40% of women worldwide were overweight in 2020.
We have shown a high cumulative prevalence of overweight and obesity among our patients. Obesity was for centuries desirable and a sign of wealth in various African countries . A traditional practice of force-feeding teenage girls (known as leblouh in our country) has indeed been prevalent in Mauritania and several other African populations [25–26].
Although lifestyle choices and low provision of healthcare services in African populations may be determinant in the disease expected development, various studies have shown that other risk factors may take part in BC prognosis such as patient race or ethnic origin, parents’consanguinityand age at onset[27–29].
The comparableearly age atbreast canceronset observed in our cohort, globally in Sub-Saharan and British black women against a relatively late age of 67 years in white British women at presentation  was in this context relevant.African-American women havealso higher rates of grade 3 than their Caucasian counterparts [30–31].
Race related differences among BC patients have been attributed to varioushereditary grounds including breast cancer susceptibility genes and endogenous hormones.For instance, in the US,the frequency of samples tested negative for receptors of progesterone,estrogen and HER2 protein (TNBC) was higher in African-American women (28%) compared to Caucasian women (12%). TheMauritanian population is composed of three main groups all Muslims but of different race origin: the white Maures (WM) speaking Hassaniya, a berber-arab dialect. This group ethnically and culturally self-identifies with the neighboring North Africa populations. The black Maures (BM) also speaking Hassaniya but share the same race origin with the third group, the black African Mauritanians (BAM), as both descended from native sub-Saharan Africans.
The global TNBC prevalence (40.4%)observed in this study was intermediate between the percentages of 28.5% in the white Moors and 71.51 % in the black Moors-black Africans group respectively. The frequency observed in the white Moors (28.5%) although slightly higher, was comparable to the percentages in North African populations [35–36].The frequencies in black Moors-black Africans group, is also similar to those reported in sub-Saharan African women-based studies[37–38] which is consistent with the common African ascendance above mentioned.
This ethnically associated repartition of percentages in TNBC also concords with the distribution of other biomarkers we reported previously in our population [39–40]. However, although differences of percentages between TNBC and NTNBC patients were observed, all parameters we analyzed did not reach the level of statistical significance set.