A 65 year-old-woman presented to our hospital for a 4 months history of pain in the left shoulder with limitation of movements. Plan radiographs showed a lytic lesion of the upper third of the left humerus without fracture (Figure 1). Magnetic resonance imaging revealed a lytic and enhancing lesion measuring 4,5×5 cm in diameter, with extension into the adjacent soft tissues and scapula. Bone scan and MRI (Figure 2). MR imaging showing destructive and enhancing mass of the humerus performed, and histopatholgic findings confirmed the diagnosis of plasmacytoma. Complete blood count, serum calcium, and creatinine were normal. Bone marrow aspirate found less than 10% monoclonal plasma cells. M-protein was absent in both serum and urine protein electrophoresis. The final diagnosis of solitary plasmacytoma was retained. The patient is actually receiving treatment by radiation therapy at the dose of 50 Gy.