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Neuroradiology Case of the Week

Case 151

Alisa Johnson, Terry Chun MD, and PL Westesson MD, DDS, PhD

Clinical Presentation: The patient is a 51-year-old male with a history of lymphoma and cervical fusion. He presents with extensive lymphadenopathy in the neck.

Radiological Findings:

Plain film: There is a huge osseous mass in the posterior aspect of C2 through C4 including three spinous processes. C4-5 facet joint is clearly visualized, however, C3-4 and C2-3 are indistinct.

CT: There is a lytic lesion extending from C2 to C4. The lesion encroaches on the spinal canal and the spinal cord, which is not visualized on this CT scan, is compressed and displaced to the left.

MRI: There is an enhancing expansile lytic mass involving the bilateral posterior elements of C2 and C3 and the right posterior elements of C4. This mass encroaches upon the spinal canal. There is resultant severe spinal canal stenosis with compression of the spinal cord from the lower aspect of the C2 vertebra to the upper aspect of the C4 vertebra. There is vague increased T2 signal intensity within the spinal cord in the region of cord compression consistent with mild edema.
     Within the central aspect of the C3 vertebral body, there is abnormal increased T2 signal intensity and enhancement suspicious for tumor involvement.

Diagnosis:  Plasmacytoma

Clinical Discussion: Solitary bone plasmacytoma affects fewer than 5% of patients with plasma cell myeloma [1]. Solitary bone plasmacytomas have a 10-year disease-free survival rate of 15-46%, and the overall median survival time is 10 years [2]. There is a male predominance with the patient generally in their sixth decade of life.
     Most patients present with back pain secondary to bone destruction by the infiltrating plasma cell tumor. [1,3]. Compression fractures of the thoracic and lumbar vertebral bodies are seen in patients with plasmacytoma and usually result in severe spasms and back pain.
     A plasmacytoma is a discrete, solitary mass of neoplastic monoclonal plasma cells in either bone marrow or a soft tissue site with no evidence of multiple myeloma elsewhere. Solitary plasmacytomas can be divided into 2 groups according to location (1) Plasmacytoma of the skeletal system (solitary bone plasmacytoma) and (2) Soft tissue plasmacytoma (extramedullary plasmacytoma). The diagnostic requirements for plasmacytoma are:

1. Solitary lesion which is biopsied and showed plasma cells
2. Negative skeletal survey, Negative MR of spine, pelvis, proximal femora/humeri
3. Negative clonal cells in marrow aspirate
4. No anemia, hypercalcemia, or renal involvement because this would suggest systemic myeloma

Neuroimaging Discussion: The best diagnostic clue for plasmacytoma is hypointense marrow with low-signal and curvilinear areas on T1WI. The most common location of a plasmacytoma is the vertebral body and there is often epidural involvement. Plain films can look normal early in the pathologic process but later will demonstrate lytic multicystic-appearing lesion sometimes with vertical dense striations. There may also be a pathologic fracture evident. ; On CT, commonly there will be a lytic and destructive lesion in the vertebral body sometime with compression fractures. Only about 3% of the time will there be osteosclerosis and even more rare is the involvement of the intervertebral disc. The T1WI find consistent with plasmacytoma is a solitary vertebral bone lesion with isointense to hypointense. T1WI with contrast often shows mild to moderate diffuse enhancement of the lesion and rarely will have peripheral enhancement. Scanning the entire spine will result in finding an additional lesion 1/3 of the time. T2WI demonstrates heterogeneous signal with focal hyperintensities and curvilinear areas of signal void. The STIR will show hyperintensities which correspond to lytic lesions on the non-contrast CT. Fat-suppressed and T2WI are helpful in delineating the extension of the lesion [5].

References:

1. Dimopoulos MA, Moulopoulos LA, Maniatis A, Alexanian R: Solitary plasmacytoma of bone and asymptomatic multiple myeloma. Blood. 2000 Sep 15;96(6):2037-44. [Medline]
2. Hu K, Yahalom J: Radiotherapy in the management of plasma cell tumors. Oncology (Williston Park). 2000 Jan;14(1):101-8, 111; discussion 111-2, 115. [Medline]
3. Kyle RA: Monoclonal gammopathy of undetermined significance and solitary plasmacytoma. Implications for progression to overt multiple myeloma. Hematol Oncol Clin North Am. 1997 Feb;11(1):71-87. [Medline]
4. Castillo, M. The Core Curriculum: Neuroradiology.  Lippincott Williams & Wilkins, Philadelphia: 2002.
5. Ross J, Brant-Zawadzki M, Chen M, Moore K, Salzman K. Diagnostic Imaging: Spine, 1st ed. Amirsys Inc: Altona, 2004.