Extraosseous plasmacytoma with an aggressive course occurring solely in the CNS.

Extraosseous (extramedullary) plasmacytoma is a relatively indolent neoplasm that constitutes 3-5% of all plasma cell neoplasms. Rare cases have been reported to truly occur in the CNS and not as an extension from a nasal lesion. EBV expression in plasma cell neoplasms has been reported in very few cases that are mainly post-transplant or occurring in severely immunosuppressed patients. We report a case of extraosseous plasmacytoma with an aggressive course in an HIV-positive individual that occurred solely in the CNS, showing EBV expression by in situ hybridization, and presenting as an intraparenchymal mass as well as in the CSF.