We present an unusual case of intracranial plasma cell granuloma in a 70-year-old man with a 6-month history of progressive visual disturbance. The lesion extensively involved the cranial base, extended into the frontal region, and reached the floor of the third ventricle in the suprasellar area. Microscopic examination of multiple diagnostic transsphenoidal biopsies showed an inflammatory proliferation with a predominance of cells that were immunohistochemically determined to be polyclonal plasma cells. Ultrastructural analysis confirmed the presence of numerous mature plasma cells in a mixed inflammatory proliferation. In situ hybridization for Epstein-Barr viral RNA revealed no evidence of viral expression. The patient was treated with steroid therapy and radiotherapy, without any appreciable reduction of the lesion's size. He is alive with persistent severe visual disturbance 14 months after the diagnosis. We discuss the etiopathogenetic, diagnostic, and therapeutic issues related to this entity, and review the literature.