MR characteristics of primary extramedullary plasmacytoma in the head and neck.

PURPOSE To define MR characteristics of primary extramedullary plasmacytoma in the head and neck using a variety of plain and contrast-enhanced MR protocols. METHODS Six patients with primary extramedullary plasmacytoma in the head and neck were examined clinically and with MR imaging at 1.5 T. The morphologic appearance and signal intensities of the lesions were analyzed and the results of the imaging findings were compared with histopathologic findings. RESULTS Qualitative analysis showed that five lesions were oval and sharply demarcated without signs of infiltration; the other lesion filled the parapharyngeal space bilaterally. On t2-weighted sequences, the lesions had moderate signal intensity. On plain T1-weighted sequences, the tumors were isointense or slightly hyperintense with respect to surrounding muscles; after administration of contrast medium, four lesions notable enhancement, with distinct central inhomogeneity. CONCLUSION Although morphologic features or evidence of contrast enhancement do not assure certain diagnosis of extramedullary plasmacytoma, these MR imaging characteristics should prompt the radiologist to include this rare lesion in the differential diagnosis.