Epithelial/myoepithelial carcinoma of breast: A report of hitherto unreported case

Abstract

Herein reported is the first case of epithelial/myoepithelial carcinoma (EMC) of breast. An 83-year-old woman noticed a circa 1.0 cm tumor of left breast. Core needle biopsies were diagnosed as invasive ductal carcinoma. Mastectomy with axillary lymph node dissection was performed, and gross examination revealed a circa 1 cm × 1 cm tumor. Microscopically, the tumor was composed of invasive malignant cells forming tubular or cords structures with a scirrhous collagenous stroma. The malignant cells were composed by the following two elements; one was malignant epithelial cells and the other was malignant myoepithelial cells with clear or vacuolated cytoplasm. Immunohistochemically, the myoepithelial element was positive for p63, CD10, cytokeratin (CK) 34BE12, and CK5/6, S100 protein and alpha-smooth muscle actin. Both elements were positive for CK7, p53, and Ki67 (labeling: 16%), estrogen receptor, progesterone receptor. Both elements were negative for CK20 and HER2/neu. The sentinel and level 1 lymph node were negative for metastasis (0/6). The tumor was pT1pN0cM0 and the stage was stage 1. The patient had booster hormone therapy and is now alive 14 months without recurrence after the operation.