Morphological characteristics of basal-like subtype of breast carcinoma with special reference to cytopathological features.

Expression profiling of invasive breast carcinomas by DNA microarray techniques has identified five distinct subtypes of tumors (luminal A, luminal B, normal breast-like, HER2 overexpression, and basal-like) that are associated with different clinical outcomes and with different chemotherapy. Basal-like carcinoma is associated with younger patient age, high histological grade, aggressive clinical course, development of distant metastasis, poor prognosis, and relatively high mortality rate. Basal-like carcinomas do not express estrogen receptor, progesterone receptor, or HER2 (triple-negative phenotype). Therefore, patients with basal-like carcinomas are not likely to benefit from endocrine therapies or trastuzumab, but are likely to benefit from systemic chemotherapy. Although genetic, morphological, and immunohistochemical features of basal-like carcinomas have been reported, there is no universal definition for those tumors. Furthermore, there are no specific morphological and immunohistochemical features that can identify those tumors in routine diagnostic materials. In the present paper, we present data of histological and cytological features of basal-like breast carcinoma, and discuss about its morphological spectrum.