Metaplastic breast carcinoma with melanocytic differentiation

Metaplastic carcinoma of the breast is a rare heterogeneous malignancy, accounting for <1% of all invasive breast carcinomas, in which adenocarcinoma is found to coexist with an admixture of spindle, squamous, chondroid or bone-forming neoplastic cells. Metaplastic breast carcinoma composed of both epithelial and melanocytic elements is rare, and only seven cases have been reported so far. Reported herein is the case of a 38-year-old woman with a nodular mass in her left breast suspicious of malignancy, discovered during routine ultrasound examination. After histological and immunohistochemical examination of the resected tumor mass, initial diagnosis was collision tumor: ductal invasive carcinoma and metastatic melanoma. The patient underwent quadrantectomy, chemotherapy and radiotherapy. At 6 years follow up the patient was alive and healthy, without local recurrence or metastases. After revising slides and the literature, in addition to patient follow up, it was concluded that this case represents metaplastic carcinoma with melanocytic differentiation.