Introduction: Little is known about the biology, molecular profile and hence optimal treatment of African Nigerian breast cancer. The aim of this work, therefore, was to characterize the histology and molecular profile of Nigerian breast cancer. Methods: Breast carcinomas from women at 6 centres of similar tribal origin in Nigeria were reviewed and assembled into tissue microarrays (TMAs), and sections were stained for hormone receptors, i.e. estrogen receptor (ER)α, ERβ1, ERβ progesterone receptor (PR) and androgen receptor, cyclin D, HER2, Ki67 and cytokeratins (CKs), i.e. CK5/6 and CK14 (basal) and CK18 and 19 (luminal). Results: A total of 835 tumours were analysed. The mean age at diagnosis was 48.62 ± 12.41 years. The most common histological subtype was ductal NST (no-special-type) carcinoma (87.3%). Over 90% of the tumours were grade 2 or 3. The predominant molecular phenotype was the non-basal, triple-negative type (47.65%) followed by the HER2-positive group (19.6%). The percentage of ER-, PR- and HER2-positive tumours was 22.4, 18.9 and 18.8%, respectively. Conclusion: Nigerian breast cancer predominantly has a high-grade, triple-negative profile. It occurs at a younger age and bears similarities at the molecular level to pre-menopausal breast cancer in white women, with remarkably lower levels of ERβ expression. The early presentation and histological and molecular phenotype may explain the poor prognosis, and tailoring treatment strategies to target this unique profile are required.

Introduction: Breast cancer outcomes vary across different ethnic groups. MicroRNAs (miRs) are small non-coding RNA molecules that regulate gene expression across a range of pathologies, including breast cancer. The aim of this study was to evaluate the presence and expression of miRs in breast cancer samples from different ethnic groups. Materials and Methods: Breast cancer tissue from 4 ethnic groups, i.e., British Caucasian, British Black, Nigerian, and Indian, were identified and matched for patients’ age, tumour grade/type, and 10 × 10 µm sections taken. Tumour areas were macrodissected, total RNA was extracted, and cDNA was synthesised. cDNA was applied to human miScript PCR arrays allowing the quantification of 84 of the most abundantly expressed/best-characterised miRs. Results: Differential expression of 9 miRs was seen across the 4 groups. Significantly higher levels of miR-140-5p, miR-194 and miR-423-5p (the last of which harbours the single-nucleotide polymorphism rs6505162) were seen in the breast tumours of Nigerian patients when compared with other ethnic groups (all p < 0.0001). miR-101 was overexpressed in breast cancers in the Indian patients. An in silico analysis of miR-423-5p showed that the AC genotype is mainly associated with Europeans (57%), while Asians display mostly CC (approx. 60%), and Africans mainly AA (approx. 60%). Conclusions: This study shows divergence in miR expression in breast cancers from different ethnic groups, and suggests that specific genetic variants in miR genes may affect breast cancer risk in these groups. Predicted targets of these miRs may uncover useful biomarkers that could have clinical value in breast cancers in different ethnic groups.