Synchronous infiltrating ductal carcinoma and primary extramedullary plasmacytoma of the breast

BACKGROUND Extramedullary plasmacytomas are seldom solitary and usually progress to diffuse myelomatosis. Plasmacytomas of the breast are rare, especially when not associated multiple myeloma. Synchronous infiltrating ductal carcinoma and primary extramedullary plasmacytoma of the breast have not previously reported. CASE PRESENTATION A 27-years-old woman with an untreated upper outer quadrant breast mass for 1-year was referred to our cancer hospital for surgical evaluation of increasing breast pain. Postoperatively, microscopic examination revealed an infiltrating ductal carcinoma complicated by an extramedullary plasmacytoma divided by fibrous tissue in one section. Following surgery, the patient received chemotherapy for the carcinoma and radiotherapy for the plasmacytoma. CONCLUSION In this case, careful histopathology examination was essential to make the correct diagnosis and therapy for these synchronous lesions. The patient finished chemotherapy and radiotherapy without significant adverse effects.