[Multiple myeloma presenting as a mass lesion in the frontal bone. Case report]

The patient, a 51-year-old male, was hospitalized for evaluation of a frontal subcutaneous mass. There were no signs of intracranial hypertension and no neurological deficit. His general medical status was normal, but he had been diagnosed as having immunoglobulin G (IgG) lambda type multiple myeloma by bone marrow aspiration and immunoelectrophoresis. A plain skull X-ray showed a large bony defect and multiple punched-out lesions in the frontal bone. Computed tomography showed an epidural high-density mass with marked homogeneous enhancement. Carotid angiography showed a hypervascular tumor fed by the bilateral external carotid arteries. At surgery, a reddish tumor was detached from the dura mater and totally resected. The pathological diagnosis was IgG lambda type plasmacytoma. After 40-Gy radiation and chemotherapy, the postoperative course over the following year was uneventful. Although the prognosis of multiple myeloma is poor, that of solitary intracranial plasmacytoma is reportedly good. However, since there is a high incidence of transition from solitary plasmacytoma to multiple myeloma, patients with intracranial plasmacytoma should be followed for a long period.