Extracranial plasma cell granuloma presenting as a diffuse meningeal and intraparenchymal mass

Plasma cell granuloma (PCG) is uncommon, characterized by polyclonal proliferation of mature plasma cells, usually within systemic organs. Only four previous cases have involved the central nervous system (CNS). This is the first reported case of an extracranial PCG and secondary involvement of the brain and meninges. Magnetic resonance imaging (MRI) disclosed a diffuse, enhancing meningeal process infiltrating the underlying brain, causing severe swelling and edema, consistent with an inflammatory, infectious, or neoplastic etiology. Examination of temporal dural biopsy specimen demonstrated PCG, consistent with the patient's original tumor. Following dexamethasone and radiation therapy, MRI and neurological findings normalized.