Mucoepidermoid carcinoma of the breast is very rare. Only 14 cases have been reported in the English language literature. All of these patients were women with ages ranging from 46 to 72 years. Five of the cases involved high-grade mucoepidermoid carcinomas and 9 were low-grade. All of the patients with low-grade mucoepidermoid carcinoma were disease-free in the follow-up period. Four patients with high-grade mucoepidermoid carcinoma died from the disease 7 to 30 months after surgery and all 4 were found to have distant metastasis. The case of mucoepidermoid carcinoma of the breast discussed here was histopathologically high-grade. The patient has remained disease-free 4 years after modified radical mastectomy and adjuvant chemotherapy. Diagnose of mucoepidermoid carcinoma of the breast is more difficult than mucoepidermoid carcinoma in the salivary gland due to possible confusion with metaplastic carcinoma or squamous cell carcinoma. Special histological stains are definitely needed for differential diagnosis.