Solitary bone plasmacytoma
Solitary plasmacytomas are localized single tumors of monoclonal plasma cells that occur in two variants: solitary plasmacytoma of bone and extraosseous plasmacytoma. Solitary plasmacytoma of bone accounts for only 1%-2% of plasma cell lesions, and extraosseous plasmacytoma is also approximately 1%. These are both very uncommon at the skull base. Welsh et al. report two cases of plasmacytic neoplasms at the skull base where the differential diagnosis included pituitary adenoma when the tumor was sellar/suprasellar, or other bone-related tumors such as chordoma/chondrosarcoma when clivus/sphenoid bones were involved. The use of cytologic preparations facilitated intraoperative diagnosis 1).
They occur as lytic lesions within the axial skeleton and extramedullary plasmacytoma (EP)s most often occur in the upper respiratory tract (85%), but can occur in any soft tissue. Approximately half of all cases produce paraproteinemia. SBPs and EPs are mostly treated with radiotherapy, but surgery is used in some cases of EP. The skeletal forms frequently progress to multiple myeloma over the course of 2–4 years.
Solitary bone plasmacytoma (SBP) may involve any bone, but they have a predisposition for the red marrow-containing axial skeleton:
see Skull plasmacytoma.
Patients with long bone involvement may present with pathologic fracture.
A report describes the extremely rare manifestation of plasmocytoma of the spinal cord itself that therefore should be considered in the differential diagnosis of spinal cord mass lesions 2).