Biopsy-proven mantle cell lymphoma in brain parenchyma.

Brain parenchymal involvement by mantle cell lymphoma is rare and confers a grim prognosis. More commonly, patients with central nervous system manifestations of mantle cell lymphoma have leptomeningeal involvement on radiographic studies with malignant cells found in the cerebrospinal fluid. Risk factors for central nervous system involvement include a high proliferation index, bone marrow involvement, and blastoid morphology. We present an unusual case of a biopsy-proven mantle cell lymphoma mass lesion in the brain parenchyma as the presentation of relapse 6 months after diagnosis.