Ki67 Expression and Its Association With Clinicopathological Factors and Intrinsic Subtypes of Male Breast Cancer in Uganda: A Cross-sectional Study

Background: Male breast cancer (MBC) is a rare disease entity globally with poor prognosis compared with female breast cancer; however, studies reporting on MBC are rare especially in resource-limited settings. Objectives: We aimed to study the expression of Ki67 and its association with clinicopathological factors and intrinsic subtypes among male patients with breast cancer (BC) from a resource-limited setting. Design: This was a cross-sectional study which included retrospective data. Methods: The study included data of 54 males with BC who were diagnosed from January 2014 to December 2024. The study was conducted at the Department of Pathology, Uganda Cancer Institute (UCI) in Kampala Uganda from February to June 2025. Data were extracted from the electronic dataset and patients’ clinical files and laboratory forms. One-way analysis of variance statistical test was used to assess the association of Ki67 absolute value (mean) with clinical and pathological factors and intrinsic subtypes of BC, followed by performing multivariable linear regression analysis for adjusting for confounding factors. Results: The mean age of the patients was 56.4 ± 15.1 years, and the youngest patient had 25 years. Majority 68.5% (38/54) of the patients had advanced disease (stage III and IV). Also, majority 68.5% (37/54) of the cases comprised of ER+, PR+, and HER2− intrinsic subtype. Only intrinsic subtypes of BC (95% confidence interval CI = 3.397-16.503, P = .032) and PR status (95% CI = 5.693-24.397, P = .042) remained the predictors of Ki67 expression after performing multivariable linear regression analysis. Conclusion: The findings of this study have shown high expression in cases of MBC which are triple negative and negative PR status. This indicates that high Ki67 expression in MBC may be used in stratification of male patients with BC based on disease aggressiveness.