Immunohistochemical study of metaplastic carcinoma and central acellular carcinoma of the breast: central acellular carcinoma is related to metaplastic carcinoma.

Metaplastic breast cancers (MBCs) [spindle cell carcinoma (SpCC), squamous cell carcinoma (SCC), and matrix-producing carcinoma (MPC)] and invasive carcinomas with central acellular zones (CACs) were analyzed with respect to biological potential by immunohistochemical analyses. Specimens from 40 patients [20 with MBCs (7 with SCC, 6 with SpCC, 5 with MPC, and 2 with mixed type)] and 20 with CACs were analyzed using antibodies to cytokeratin (CK) 8, 5/6, 14, AE1/AE3, 34αE12, involucrin, c-kit, vimentin (VIM), alpha-smooth muscle actin, p63, epidermal growth factor receptor, epithelial cell adhesion molecule, and estrogen receptor (ER)/progesterone receptor (PR)/HER2. Expression of CK5/6, 34βE12, VIM, nuclear p63, and cytoplasmic p63 was significantly higher with MBCs than CACs (38%/13%, 70%/43%, 85%/33%, 68%/40%, and 48%/18%, respectively). Other markers were expressed at various levels in these tumors, but the difference between them was not significant. Eighteen MBC and 8 CAC cases were triple (ER/PR/HER2) negative; 17 MBCs and 7 CACs were basal-like tumors. Several differences were seen in MBCs and CACs, but they were heterogeneous, differentiating multipotentially into mesenchymal, myoepithelial, basal-like phenotypes with "stem cell-like" features. Thus, CACs are related to MBCs by immunohistochemical analyses as well as according to morphological findings.