Multiple myeloma complicated by skull plasmacytoma discovered after head injury.

Plasmacytoma is a malignant tumor originating from the plasma cells of the bone marrow. Those discovered after a head injury is rare. We report a case of a 48-year-old female who complained of scalp mass without other symptoms after head injury. Meningioma was considered preoperatively based on imaging findings, and surgical resection was performed. Postoperatively, multiple myeloma complicated by skull plasmacytoma was diagnosed by histopathology and systematic examinations in succession. When evaluating a head mass that appeared after a head injury, plasmacytoma should be considered at times. Osteolytic changes and biconvex form on imaging are beneficial to differentiation.