Solitary bone plasmacytoma (PET-CT)

Case contributed by Dalia Ibrahim
Diagnosis certain


Back pain. MRI revealed D6 marrow infiltrative lesion, likely metastatic. For PET-CT to assess for the primary tumor.

Patient Data

Age: 60 years
Gender: Male



FDG avid expansile lytic lesion involving D6 vertebra including its pedicles, transverse and spinous processes with SUV max 27. It shows coarse bone trabecula and thinned out cortex giving the characteristic "mini-brain" appearance. It shows small extra-osseous soft tissue sheets.

No metabolically active lesions were distinctive for neoplasia in the rest of the body.

Radiological findings are suggestive of solitary bone plasmacytoma.

The first image shows excisional biopsy of the osseous and extra-dural lesion showing plasma cell myeloma.

The second image shows the hypermetabolic expansile lytic lesion of D6 vertebra showing thick trabecula and thinned cortex giving the mini-brain sign.

Case Discussion

The case showed typical features of solitary bone plasmacytoma with FDG avid expnasile lytic lesion involving D6 showing coarse trabecula and thinned out cortex, giving the "mini-brain" appearance. No evidence of other malignancy throughout the body.

Plasmacytomas are solitary tumors of neoplastic monoclonal plasma cells in either bone or soft tissue (extramedullary). There's minimal or no systemic bone marrow involvement, in contrast to multiple myeloma.

Solitary plasmacytomas can be divided into two groups according to the location:

  • extramedullary plasmacytoma 
  • solitary bone plasmacytoma, in which there's solitary bone involvement. It has a predilection to the axial skeleton, mainly the spine, the thoracic vertebrae are the most commonly involved, followed by the lumbar, sacral, cervical vertebrae, ribs, sternum, scapula, and clavicles.

Radiological features of solitary bone plasmacytoma include expansile lytic lesion with coarse bony trabeculation and thinned out cortex giving the "mini-brain" appearance.

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