Mucoepidermoid Carcinoma of the Breast Found during Treatment of Lymphoma

A 71-year-old woman, previously treated for malignant lymphoma, was admitted to our hospital with a tumor in the right breast. The tumor size was 2.0 cm in diameter, and the borderline was unclear. The core needle biopsy material revealed an invasive adenocarcinoma with metaplastic change. Right mastectomy and sentinel lymph node biopsy was performed. Histologically, the tumor was composed of mucus-secreting, epidermoid, and intermediate cells. These findings confirmed the diagnosis as mucoepidermoid carcinoma (MEC) of the breast. MEC is more frequently observed in the salivary glands and occurs rarely in the breast, with an incidence of approximately 0.3% of all breast cancers. Because of the rarity of the disease, the clinicopathological features and clinical outcome have not been fully investigated. The relationship between MEC of the breast and lymphoma are unclear. Here we report a rare case of MEC of the breast.