Cytology to More Clearly Distinguish Solitary Plasmacytoma at the Skull Base.

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. We 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. Intraoperative diagnosis was facilitated by the use of cytologic preparations.