Clear cell myoepithelial carcinoma of the breast: a case report.

Primary clear cell myoepithelial carcinoma (CCMC) is extremely rare. During the past twenty years, only one CCMC case has been reported. Here, a case of CCMC is reported. A 30-year-old woman became aware of an abnormal mass on the left breast, and quadrantectomy was performed. Microscopically, it consisted of tumor cells that had clear cytoplasm and showed an invasive growth pattern. Immunohistochemically, the tumor was positive for alpha-smooth muscle actin, S-100, partly positive for vimentin and epithelial membranous antigen. From these findings, the tumor was diagnosed as CCMC. Most of the clear cell myoepithelial tumors are probably misclassified in other examples. It is expected that the numbers of CCMC may be increased by routinely performing special stains and immunohistochemical stains, even without ultrastructual study.