Immunohistochemical heterogeneity of breast carcinomas negative for estrogen receptors, progesterone receptors and Her2/neu (basal-like breast carcinomas)

Basal breast carcinomas triple negative for estrogen receptors, progesterone receptors and Her2/neu breast carcinomas are more aggressive than conventional neoplasms. We studied 64 cases with immunohistochemistry, using 23 antibodies, to characterize diverse pathological pathways. A basal cytokeratin was identified in 81% of tumors and vimentin was identified in 55%. The mean Ki67 index was 46% ( range, 10-90%). Coincident expression of p50 and p65, which suggests an active nuclear factor-kappa B factor, was present in 13% of neoplasms. Epithelial growth factor receptor ( EGFR), insulin-like growth factor-I receptor ( IGF-IR) or c-kit ( CD117) was identified in 77% of tumors. Loss of protein tyrosine phosphatase was found in 14%, whereas Akt activation was present in 28%. Several differences were identified between two subtypes of basal breast carcinomas: the pure variant ( negative S-100 and actin) was more frequently associated with 'in situ carcinoma' ( P = 0.019) and pBad overexpression ( P = 0.098), whereas the myoepithelial variant ( positive S-100 or actin) showed more frequent tumor necrosis ( P = 0.048), vimentin expression ( P = 0.0001), CD117 expression ( P = 0.001) and activated caspase-3 ( P = 0.089). IGF-IR could be as important as EGFR for the growth of these neoplasms. Basal cell carcinoma has at least two subtypes with distinct microscopic and immunohistochemical features.