Imaging features of solitary extraspinal plasmacytoma

Objective: To assess the imaging features of solitary extra-spinal plasmacytoma. Methods: The imaging studies of 22 patients with histologically confirmed solitary extra-spinal plasmacytomas were retrospectively analyzed. Results: On radiographs and CT, the lesions were expansile and lytic with well-defined margins, cortical thinning or erosion, no calcification or sclerotic rim. Residual bone trabecula was present in 11 patients whereas irregular periosteal reaction was found in only 1 patient. On MRI, 14 tumors were slightly T₁ and T₂ hyperintense relative to muscle or brain with homogenous enhancement and no necrosis. The lesions showed an infiltrative growth pattern. Associated soft-tissue mass was noted in 2 and peritumoral marrow edema in none. 63.6% (14/22) of the tumors were misdiagnosed as lymphomas (5), giant cell tumors (4), fibrosarcomas (2), metastases (2) and chordoma (1). Conclusion: Most of the solitary extraspinal plasmacytomas have some specific imaging features, especially on MRI. However, differentiation from primary and secondary bone tumors may be difficult. (authors)