Abstract
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<0.05 considered significant.
Results: TNBC was the most prevalent subtype (33.7%), followed by Luminal A (20.5%), Luminal B (HER2+) (16.1%), HER2-enriched (16.1%), and Luminal B (HER2−) (13.6%). Infiltrating duct carcinoma (NOS) accounted for 85.3% of cases. A significant association was observed between age group and molecular subtype (χ² = 14.36, df = 8, p = 0.023). No significant relationship was found between molecular subtype and histologic grade (p = 0.149). The Ki-67 index was high (≥20%) in 41% of tumors.
Conclusion: The predominance of aggressive subtypes, particularly TNBC, highlights an urgent need to integrate routine molecular classification into breast cancer diagnostics in Nigeria. IHC-based profiling is a practical tool for improving risk stratification and guiding individualized therapy in resource-limited regions.
Keywords
Breast cancer, Molecular subtypes, Immunohistochemistry, Estrogen receptor, HER2, Triplenegative breast cancer, Ki-67, Nigeria