A case of high-grade mucoepidermoid carcinoma of the breast with a dominantly epidermoid component is presented. The tumour was biochemically oestrogen and progesterone receptor negative. Though the primary tumour was small (1 cm) and without axillary lymph node metastases at mastectomy, the clinical course was rapid. Despite radio-, chemo- and hormonal therapy the patient died 25 months after mastectomy with widespread systemic disease. The metastatic pattern was that of typical breast carcinoma despite the unusual histological appearance of both primary and metastatic tumour tissue.