Age / Sex : 54 / F

Chief complaint: Cervical pain

What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(답안은 한 개만 보내주시기 바랍니다)

Courtesy: 김여주 (Yeo Ju Kim) 인하대병원 (Inha University Hospital)

Plasmacytoma

Discussion

Findings:

On a axial CT image, there is a osteolytic lesion in a vertebral body. It is partially surrounded by curvilinear sclerotic rims but has a cortical destruction at posterior wall of the vertebral body.

On MRI, The osteolytic lesion show low signal intensity on T1 weighted image and high signal intensity on T2 weighted image. After injecting contrast materials, this lesion show homogeneous enhancement. This lesion is surrounded by curvilinear low signal intensity, corresponding with the sclerotic rims on CT, resembling sulci of brain on all sequences (so called minibrain sign).

Differential Diagnosis:

osteolytic metastasis, osteoblastoma, giant cell tumor, hemangioma, Paget’s disease, Chronic osteomyelitis

Diagnosis:  

Plasmacytoma

Discussion:

A solitary bone plasmacytoma has a predisposition for the red marrow-containing axial skeleton. It is a single lytic lesion without signs of myeloma cells on bone marrow examination. The thoracic vertebrae are most commonly involved, followed by lumbar, sacral, and cervical vertebrae. The rib, sternum, clavicle, or scapula is involved in 20% of cases. The peak incidence is in the 4^th to 6^th decades, and it is more common in males.

- Diagnostic criteria

• Single area of destruction due to clonal plasma cells


• Bone marrow plasma cell infiltration <5% of all nucleated cells


• Absence of osteolytic bone lesions or other tissue involvement (i.e. no evidence of myeloma)


• Absence of anemia, hypercalcemia or renal impairment (usually attributable to myeloma)


• Low or absent serum / urine monoclonal protein


• Preserved levels of uninvolved immunoglobulins

Mini brain sign represents cortical thickening and is most likely caused by lytic lesions. The thickened struts resemble sulci in the brain, leading to a small brain appearance. A “spoke-wheel” pattern has also been described. Mini brain sign is considered highly specific for solitary plasmacytoma. The characteristic appearance of thickened cortical struts of minibrain sign is probably a result of a stress phenomenon from the lytic process of the plasmacytoma forcing the remainder of the bone to increase thickness as a compensatory response to weakening bone. This “minibrain sign” is not seen in other primary bone or metastatic spine lesions, concerns the less aggressive nature of plasmacytoma compared with other tumors that destroy bone. Therefore, a mini brain appearance in an expansile lesion of the vertebral body could be sufficiently pathognomonic of solitary plasmacytoma. 

References:

1. Dimopoulos MA, Kiamouris C, Moulopoulos LA. Solitary plasmacytoma of bone and extramedullary plasmacytoma. Hematol. Oncol. Clin. North Am. 1999;13 (6): 1249-57.

2. Ooi GC, Chim JC, Au WY et-al. Radiologic manifestations of primary solitary extramedullary and multiple solitary plasmacytomas. AJR Am J Roentgenol. 2006;186 (3): 821-7.

3. Major NM, Helms CA, Richardson WJ. The "mini brain": plasmacytoma in a vertebral body on MR imaging. AJR Am J Roentgenol. 2000;175 (1): 261-3.

4. Kasliwal MK, O’Toole JE. Unique radiologic feature of spinal plasmacytoma: mini-brain appearance. Neurol India 2011;59:486–487.

5. Subhas N, Bauer TW, Joyce MJ, Sundaram M. The “minibrain” appearance of plasmacytoma in the appendicular skeleton. Skeletal Radiol 2008;37:771–774.

6. Luiz Alves Ferreira-Filho, José Luiz Pedroso, Eduardo A.H. Sato, et al. Teaching NeuroImages: ''Mini brain'' sign: A radiologic marker for vertebral solitary plasmacytoma.Neurology 2014;82;e210-e211