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.
CASE REPORTA 74-year-old woman undergoing chemotherapy for relapsing multiple myeloma (subtype IgG Lambda) presented to her medical oncologist with a new palpable right breast lump. A screening mammogram four months prior was interpreted as normal and given a BI-RADS Category 1 (negative) final assessment (Figure 1). Kappa free light chains were significantly decreased at 0.17 mg/dL (normal 0.33 -1.94 mg/dL) and Lambda free light chains were significantly elevated at 197 mg/dL (normal 0.57 -2.63 mg/dL). Clinically, the patient had persistent whole-body aches, oral bleeding, and bone pain. The patient was then referred to the breast imaging service for further work-up. She underwent a diagnostic right mammogram which showed two well-circumscribed hyperdense massesthere were no suspicious calcifications, nipple retraction, skin thickening, or areas of architectural distortion (Figure 2). A same-day ultrasound demonstrated two mixed echogenic masses with ill-defined margins and increased vascularity (Figure 3). Primary differential considerations included plasmacytoma and primary breast cancer. Hematoma was initially considered as the patient was on anticoagulation for deep venous thrombosis prophylaxis. However, given the presence of vascularity, it was deemed unlikely. An infectious etiology (i.e., breast abscess) was also considered given the rapid increase in size over four months. This was thought to be unlikely with no clinical signs of infection and central rather than peripheral vascularity. A microscopic examination of an ultrasound guided biopsy yielded plasma cell neoplasm (Figure 5). A follow-up PET/CT
