A Case of Plasma Cell Myeloma Presenting with a Huge Ulcerating Breast Mass

Plasma cell myeloma (PCM) of the breast is extremely unusual. It probably constitutes 0.7% of extramedullary plasmacytomas, and 0.2% of all breast malignancies. Clinically and radiologically, PCM of the breast is indistinguishable from breast carcinoma or other primary breast disorders. Therefore, histomorphological examination with immunohistochemistry are considered as gold standards for its diagnosis in tissue samples. We report a case of a 30-year-old female presented with a progressive huge ulcerating left breast mass, despite chemotherapy. She had a history of an initially misdiagnosed humeral lytic lesion, and recurrent lytic boney lesions for the past 7 years. Positive CD138, CD56 and Kappa immunostaining has confirmed PC differentiation and monoclonality of the tumor cells. Subsequently, PCM of breast was diagnosed and the patient was transferred for chemotherapy and follow-up.