Histological and Molecular Subtyping of Breast Cancer with Epstein–Barr Virus LMP1 Expression among Northern Nigerian Women: A Combined Survey

Epstein–Barr virus (EBV) has been linked to several cancers, but its involvement in breast cancer is not well understood in sub-Saharan Africa. This study examined the sociodemographic, lifestyle, and reproductive health characteristics of women in Katsina and Kaduna States, Nigeria, and investigated histological and molecular subtypes of breast cancer with attention to EBV latent membrane protein 1 (LMP1) expression. Methods: Three hundred and twenty-five confirmed breast cancer cases were reviewed. Questionnaire data were used to capture sociodemographic, lifestyle, and reproductive factors. Histological classification was carried out on all cases, while immunohistochemistry was performed on 91 and 63 samples to determine molecular subtypes and EBV LMP1 expression resoectively. Odds ratio analysis of EBV exposure and breast cancer risk in Africa was drawn from pooled data. Results: Most participants were married housewives with limited education. Differences between states were observed in education, physical activity, contraceptive use, and cultural habits such as grooming kit sharing and communal eating. Almost all women avoided smoking and alcohol, ate vegetables regularly, breastfed, and reported no current pregnancy. Invasive ductal carcinoma was the most frequent histological subtype in both Katsina (81.2%) and Kaduna (84.0%), with no significant differences between them. Of the 91 cases analyzed by immunohistochemistry, the triple-negative molecular subtype was most common (47.2%), followed by HER2-positive (35.8%). EBV LMP1 expression was not detected in any of the samples. Odds ratio analysis, however, showed a strong association between EBV exposure and breast cancer risk in Africa (OR = 24.17, 95% CI: 12.46–46.87, p<0.0001). The absence of LMP1 expression prevented biomarker correlation. Conclusion: Breast cancer in Northern Nigeria is mainly invasive ductal carcinoma and most frequently triple-negative in molecular profile. While EBV exposure appears strongly associated with breast cancer risk in Africa, the lack of detectable LMP1 expression suggests latent infection or protein suppression, limiting its value as a biomarker. Further molecular studies are needed to clarify the role of EBV in breast cancer development. Keywords: Epstein–Barr virus (EBV), Breast cancer, Immunohistochemistry, Histological types, Moleculer subtyping, Scarff-Bloom Richardson Grading.