Extramedullary Plasmacytoma of the breast in a patient with Multiple Myeloma

Extramedullary plasmacytoma of the breast is rare. It is important to recognize the imaging findings and include it as a differential consideration in multiple myeloma patients with a breast mass. A 74-year-old woman undergoing chemotherapy for relapsed multiple myeloma presented with a palpable mass in her right breast. A screening mammogram four months prior was unremarkable. She underwent a diagnostic right mammogram which showed two well-circumscribed hyperdense masses. An ultrasound of the right breast showed mixed echogenic masses with indistinct margins and increased vascularity. Ultrasound guided biopsy confirmed the presence of an extramedullary plasmacytoma. A follow-up whole body PET/CT demonstrated an FDG-avid right breast mass with extensive osseous metastases.