A rare case of basal cell adenoma of the breast

A 71-year-old woman was referred to our hospital for further evaluation after a breast cancer screening examination. Ultrasonography revealed a hypo-echoic mass in the left breast. Fine needle aspiration cytology revealed clusters of small, short spindle cells without atypia, suggesting a benign epithelial lesion. After 7 years of follow-up examinations, the tumor became enlarged and was excised for diagnostic confirmation. The left breast tumor histologically showed a lobulated mass encapsulated by fibrous tissues. The tumor was 1.3 cm in diameter and included cystic formations in the central area. Microscopically, two types of epithelial cells formed double-layered structures with stromal components. The tumor was histologically similar to a salivary basal cell adenoma and was definitively diagnosed as basal cell adenoma of the breast. Awareness of the possibility of salivary gland-type tumors arising in the breast will be useful when diagnosing breast tumors.