Primary large B-cell lymphoma of the fourth ventricle.

We present a patient with an isolated primary central nervous system lymphoma (PCNSL) of the fourth ventricle. A 77-year-old man had a 1 week history of intermittent vertigo, nausea, vomiting, and progressively unsteady gait. CT scans of the brain showed a fourth ventricle tumor. MRI revealed a 2.5 cm dumbbell-shaped avidly-enhancing tumor in the fourth ventricle. Metastasis or high-grade glioma was suspected. The neuropathological findings were compatible with a diffuse large B-cell lymphoma. A slit lamp examination, bone marrow biopsy, and imaging studies for extracranial lesions were unremarkable. We suggest that PCNSL be listed in the differential diagnosis of fourth ventricle tumors with well-circumscribed margins and homogenous contrast enhancement.