Comparative Study of Metaplastic Breast Carcinoma and Triple-Negative Breast Carcinoma Using Histologic and Immunohistochemical Analyses

Background : Metaplastic carcinoma of the breast is a rare subtype of breast cancer, which is characterized by estrogen receptor/progesterone receptor and HER2 negativity. Methods : Tissue specimens from 60 metaplastic breast cancer and 60 triple-negative breast cancer patients diagnosed at a single institution between 1995 and 2009 were analyzed. Immunohistochemistry for caveolin-1 (CAV-1), vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), c-kit, p53, Ki-67, breast cancer type 1 susceptibility protein (BRCA1), cytokeratin (CK) 14, and CK17 were performed on both retained tissue sets. Results : Of the 60 metaplastic carcinomas, 15 tumors (25%) exhibited spindle cell component, 27 (45%) exhibited chondroid differentiation, and 18 (30%) exhibited squamous areas. Compared to triple-negative carcinomas, metaplastic carcinomas significantly more frequently expressed CK14 (p < 0.0001), CK17 (p = 0.002), EGFR (p < 0.0001), CAV-1 (p < 0.0001), and VEGF (p = 0.029). However, expressions of BRCA1, p53, c-kit, and Ki-67 were not significantly different between both groups. Conclusions : The expression profile of metaplastic carcinoma of the breast is more homogeneous than that of other triple-negative tumors and frequently over-expresses basal markers, CAV-1, and VEGF. A typical "basal-like" phenotype and frequent expressions of CAV-1 and VEGF may justify specific therapeutic approaches.