The study of possible ethnic differences in breast cancer has mainly occurred in the United States . Recently, new data have been described for Arab populations, but the true prevalence of breast cancer remains uncertain [4, 13–17]. For the majority of these studies, which were performed only on indigenous populations, some clinicopathological features are repeatedly observed: the age of cancer presentation is a decade earlier than in European or US patients, the average size of the lesions is often greater than 20 mm, and the grade of tumors is often higher. Interestingly, these data were corroborated in our study of Arab/Moroccan immigrants. Indeed, in our series, the mean age of presentation of breast cancer was 49 years old in Moroccan patients and occurred almost a decade earlier than in European patients (mean age: 60 years old; p = 0.00001) (Table 1). These data are similar to those recently published by Chouchane et al. in a review article, in which the mean age of presentation of breast cancer for Arab patients was 48 years old, compared to 63 years old in European women. These authors also observed that two-thirds of the Arab patients with breast cancer are younger than 50 years old . We found similar results with our Arab immigrant population. Indeed, 61% of the Arab patients with cancer were less than 50 years old, compared to only 24% in the European population (p = 0.0001) (Table 2). However, these results should be interpreted with caution as they may simply reflect that the immigrant population is on average younger than the European population and that the Arab older patients have a different perception of breast cancer and therefore do not participate in the screening program. These challenges and barriers to breast cancer screening in Arab women have been demonstrated in several studies [17–19].
The second observation on Arab patients frequently found in the literature is the presence of larger tumors (mean tumor size greater than 20 mm) and a higher grade (grade 3) at diagnosis [20, 21]. We were able to confirm these findings in the general population used in our study. Indeed, over 50% of the Arab patients had tumors larger than 20 mm, compared to 38% of the European patients with a tumor greater or equal to 20 mm (p = 0.04). Furthermore, the average tumor size was 25 mm in the Arab patients, while it was only 19 mm in Europeans (p = 0.008) (Table 1). We also demonstrated that the Arab patients had an increased incidence in grade 3 tumors (p = 0.01) and fewer grade 1 tumors (p = 0.01) than Europeans.
However, the data concerning the tumor size and grade are only statistically significant in the general population, with all ages combined. Indeed, if we restrict our analysis to the premenopausal women under 50 years old, the differences in the tumor size and grade are less obvious (Table 2). This phenomenon is consistent with recent publications that establish a strong link between age at diagnosis and the size and/or grade of the tumor [7, 22]. Molecular subtyping of breast cancer gene expression has resulted in a better understanding of breast carcinoma and several distinctive breast carcinoma molecular subtypes have been identified [22, 23]. In addition to this gene expression analysis, immunohistochemical surrogates have been used for breast cancer classification with relatively good reproducibility . In the present work, we demonstrated that the luminal subtype B was the most common in an Arab/Moroccan immigrant population. This subtype was found in 56% of the women in the general population but only in 40% of the European women (p = 002) (Table 1). In contrast, the luminal A subtype was significantly more common in the European (46% than in the Arab patients (23%; p = 0.001). Interestingly, these statistically significant differences in the incidence of luminal A and B subtypes between the two populations were also seen in patients under 50 years old (Table 2). However, no differences were observed for the subtypes HER2 and triple negative. Our results corroborate the study performed on a native population in Morocco, where the luminal B subtype was also the most common . Deregulation in both genomic and/or proteomic expression of cytokeratin 8/18 and TFAP2C (a member of the AP-2 family) has been shown to regulate expression of the ER, and the RET proto-oncogene might contribute to the high proportion of the luminal B subtype observed in Arab women. However, this observation should be confirmed in future studies .