Solitary plasmacytoma of skull: a rare cytological diagnosis.

Solitary Plasmacytoma of the Skull (SPS) is very rare and only 35 cases have been reported in the English literature. It remains controversial whether a solitary plasmacytoma of the skull is essentially identical with a Solitary Plasmacytoma of Bone (SPB) or not. A solitary plasmacytoma of bone, which includes a solitary plasmacytoma of the skull, is characterized by a radiologically solitary bone lesion, neoplastic plasma cells in the biopsy specimen, fewer than 5% plasma cells in bone marrow, less than 2.0 g/dl monoclonal protein in the serum when it is present and a negative urine test for Bence Jones protein (monoclonal light chain). A solitary plasmacytoma of bone tends to disseminate or progress to multiple myeloma, even as long as 7-23 years after its presentation.