IMMUNOHISTOCHEMICAL PROFILING OF MMR PROTEINS, HER2NEU, AND BRAF MUTATIONS IN COLORECTAL CARCINOMA: CORRELATIONS WITH CLINICOPATHOLOGIC FEATURES IN AN INDIAN COHORT

Background: Colorectal carcinoma (CRC) is one of the most prevalent malignancies globally, influenced by genetic and molecular factors such as mismatch repair (MMR) protein deficiency, HER2neu overexpression, and BRAF mutations. Objective: To evaluate immunohistochemical expression of MMR proteins, HER2neu, and BRAF mutations in colorectal carcinoma and to correlate these with clinicopathologic features. Methods: A cross-sectional study on 100 surgically resected CRC specimens was performed. IHC for MLH1, MSH2, MSH6, PMS2, HER2neu, and BRAF V600E was conducted. Correlations with tumor site, grade, and stage were analyzed. Results: MMR deficiency was observed in 17% of cases, HER2neu overexpression (3+) in 7%, and BRAF mutation in 12%. MMR-deficient tumors were predominantly right-sided and had increased tumor-infiltrating lymphocytes. HER2neu overexpression correlated with higher stage and vascular invasion, while BRAF mutation was associated with poor differentiation and right-sided tumors. Conclusion: MMR deficiency and BRAF mutation define distinct biological subsets of CRC, while HER2neu positivity indicates potential candidates for targeted therapy. Integration of molecular profiling in CRC diagnosis aids in prognostication and personalized treatment.