Triple-Negative Breast Carcinoma Subtyping by Immunohistochemistry – Our Experience

Context: Breast cancer is currently treated according to the subtype determined by the expression of three immunohistochemical markers, namely, estrogen receptor, progesterone receptor, and human epidermal growth factor 2 neu receptor. If all three markers are negative, the subtype is triple-negative breast carcinoma (TNBC). This subtype is a molecularly heterogeneous group expressing different genetic signatures. The present retrospective observational study has used immunohistochemistry as a practical method to document different subtypes of TNBC. Materials and Methods: One hundred cases of TNBC were studied at a tertiary cancer care center, using a panel of five markers – androgen receptor, cytokeratin 5/6, epithelial cadherin, epidermal growth factor receptor, and vimentin. Statistical Analysis: Monte Carlo significance test for Chi-square was used for statistical analysis. Results: One hundred patients of TNBCs were subtyped into five groups – luminal androgen receptor, basal-like one, basal-like two, mesenchymal stem-like, and unclassified. These subgroups did not differ significantly in clinicopathological characteristics except tumor size. Conclusion: TNBC is a molecularly diverse group showing many subtypes. Clinical follow-up of all these cases may reveal differences in the prognosis and survival among the subgroups.