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Neuroradiology Case of the Week

Case 383

February 2009

Jerry Lee, MD

Clinical Presentation: Patient is a 55-year-old male with monoclonal gammopathy.

Imaging Findings: Axial CT of the cervical spine demonstrates an expansile cystic mass arising from the C2 vertebral body. No evidence of cortical breakthrough or paravertebral soft tissue involvement. Sagittal MRI T1 and T2 weighted images demonstrate the expansile cystic mass at C2 which extends into the bilateral pedicles and odontoid process.

Diagnosis: Plasmacytoma

Discussion: Plasmacytoma, also called solitary myeloma, is a solitary monoclonal plasma cell tumor of bone or soft tissue, with no evidence of multiple myeloma lesions elsewhere. Multiple monoclonal plasma cell tumors are call multiple myeloma. Multiple myeloma is the most common primary malignant bone tumor and originates in the bone marrow seen between the fifth and seventh decades. It is more frequent in men than women. The axial skeleton (skull, spine, ribs, and pelvis) are the most commonly affected sites of multiple myeloma, but can involve any bone. Plasmacytoma is most commonly found in the spine. On CT imaging, plasmacytoma is commonly a lytic, destructive lesion often presenting with compression fracture and possibly associated soft tissue mass. Post-contrast imaging demonstrates little to no detectable enhancement. T1-weighted MR images are the best diagnostic imaging sequences for diagnosis and present with hypointensity and may contain curvilinear low signal areas. The posterior elements are involved in most cases. T2-weighted MR images demonstrate increased signal. There is mild to moderate diffuse enhancement with gadolinium. Bone scintigraphy is unreliable as myeloma can present with intense uptake or no uptake. PET scan can reliably detect active multiple myeloma. Differential diagnosis of a solitary osteolytic lesion of the spine includes giant cell tumor, osteoblastoma, lytic metastasis, hemangioma, and aneurysmal bone cyst.

References:

1. Ross J, Brant-Zawadzki M, Chen M, et al. Diagnostic Imaging: Spine. Amirsys, 2004.
2. Greenspan A. Orthopedic imaging: a practical approach, 4th ed. Philadelphia, Lippincott Williams and Williams, 2004: 734-39.