Breast Carcinoma: Correlation of Molecular Subtypes with Histopathologic Characteristics

Abstract

Context: Breast carcinoma is a heterogenous disease and similar histological subtypes may exhibit different behavior and treatment response. The molecular classification may provide better prognostic, predictive and therapeutic information than histological classification. The study aimed at evaluating the distribution of molecular subtypes of breast cancer and its association with prognostic factors. Method: This prospective cross-sectional study was conducted on breast cancer cases, over a period of 2 years, at M.S. Ramaiah Medical College and Hospitals, Bengaluru. The resection specimens were evaluated for histopathological features. Immunohistochemical analysis for ER, PR, Her2neu and Ki-67 expression was performed to identify molecular subtypes. Correlation of molecular subtypes with histopathological prognostic factors was done by Chi- square test or Fischer’s exact test. Results: A total of 85 cases were evaluated and classified into Luminal A (50.6%), Basal like (27%), Luminal B (11.8%) and HER-2 enriched (10.6%) molecular subtypes. Invasive ductal carcinoma was the commonest histologic type across all the molecular subtypes. Majority of low-grade tumors were Luminal A and most of high-grade tumors were Basal like (p= 0.004). HER-2 enriched and Basal like tumors were relatively more frequent in ≤ 50 years of age and Luminal A tumors exhibited less frequent lymph node metastasis. However, these associations fell short of statistical significance. Conclusion: Luminal A tumors are the most common molecular subtype. Statistically significant correlation exists between histologic grade and molecular subtype. There is no significant correlation between molecular subtype and age, tumor size, nodal metastasis, pathological T stage and TNM stage. Keywords: Basal like, Breast carcinoma, HER2­Enriched, Luminal A, Luminal­ B, Molecular subtypes