Presentation
Back pain.
Patient Data
FDG-avid lytic lesion involving L1 vertebra with SUV max 35. The vertebra shows cortical thinning and coarse bony trabeculations, giving the mini-brain sign". It's associated with extra-osseous thin soft tissue sheets. It also shows vertebral compression edge fracture.
No other metabolically active lesions were distinctive for neoplasia.
Radiological findings are suggestive of solitary bone plasmacytoma.
L1 marrow infiltrative lesion eliciting low T1 signal and heterogenous signal on T2 WI with post-contrast enhancement. It shows a coarse bone trabecula and a thinned-out cortex, giving the characteristic "mini-brain" appearance. It shows small extra-osseous enhancing soft tissue sheets. Vertebral structural collapse is noted. Mild leptomeningeal thickening and enhancement post interventional or inflammatory sequel.
A CT-guided biopsy revealed plasma cell myeloma.
Metabolically active lytic lesion involving L1 vertebra showing cortical thinning and coarse trabeculae giving the mini-brain sign, characteristic of solitary bone plasmacytoma.
Case Discussion
The case shows the typical appearance of the mini-brain sign. In fact, this appearance is so characteristic that it may obviate the need for a diagnostic biopsy.
Plasmacytoma has two subgroups:
Solitary bone plasmacytomas are uncommon plasma cell tumors that are localized to the bone. They may involve any bone, but they have a predisposition for the red marrow-containing axial skeleton; spinal disease mainly affects the thoracic vertebrae, followed by the lumbar, sacral, and cervical vertebrae, and less commonly the rib, sternum, clavicle, or scapula.
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