Molecular subtypes of breast cancer in Nigeria: clinicopathological insights from immunohistochemical profiling

Background: Breast cancer demonstrates substantial molecular heterogeneity that influences prognosis and therapeutic decisions. Immunohistochemistry (IHC) provides an accessible surrogate method for molecular classification in low-resource settings. This study evaluated the distribution and clinicopathological significance of IHC-defined molecular subtypes among breast cancer cases in a Nigerian population. Methods: A retrospective cross-sectional study was conducted on 273 histologically confirmed breast cancers diagnosed between 2019 and 2025. Formalin-fixed, paraffin-embedded tissues were stained for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67. Tumors were categorized into Luminal A, Luminal B (HER2−), Luminal B (HER2+), HER2-enriched, and Triple-Negative Breast Cancer (TNBC). Statistical analysis was performed using SPSS version 27. Associations between molecular subtype and clinicopathological parameters were evaluated using Chi-square tests, with p