ORIGINAL ARTICLE: Immunohistochemical identification of basal‐like breast carcinoma and Its histopathologic correlation

Background and aim: DNA expression profiling studies of breast cancer have identified subtypes including luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) overexpression, and basal-like type. Among them, the basal-like type was associated with poor outcome. The purpose of this study was to classify breast carcinoma by immunohistochemistry and evaluate its characteristic histopathologic features. Methods: One hundred and four cases of resected infiltrating ductal carcinoma were immunostained for estrogen receptor, HER2, cytokeratin 5/6 and p63 to classification, and basal-like subtype were evaluated for its histopathologic characteristics. Results: The prevalence of subtypes was luminal A 48.1%, luminal B 24.0%, HER2 overexpression 11.5%, normal breast-like 4.8%, and basal-like 11.5%. There was significant correlation between the basal-like type and histologic grade. And it was significantly associated with several morphological features including expanding growth pattern, presence of tumor necrosis and peritumoral lymphocytic infiltration. Conclusions: The results of this study showed that the basal-like type occupied 11.5% of infiltrating ductal carcinoma and was associated with expanding growth pattern, presence of tumor necrosis and peritumoral lymphocytic infiltration.