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.