Primary Central Nervous System Extranodal Natural Killer/T-Cell Lymphoma, Nasal Type Colliding with Meningioma.

Background: Collision tumors are defined as coexistence of 2 histologically different neoplasms occurring in the same anatomic location. Such co-occurrence of tumors in the brain is uncommon. To our knowledge, meningioma colliding with extranodal natural killer/T-cell lymphoma has not been described previously.

Case Description: A 50-year-old man presented with a 1-year history of progressive memory decline and 2 weeks of drowsiness, bradykinesia, and aphasia. Magnetic resonance imaging revealed a heterogeneously enhanced mass beside the left frontal cerebral falx resulting in midline shift. The left frontal lobe mass was resected. Pathologic examination showed the tumor consisted of whorled spindle cells and diffuse medium-sized lymphoid cells. The spindle cells were positive for epithelial membrane antigen and negative for S-100. The lymphoid cells expressed CD3ε, CD56, TIA-1, and granzyme B. Epstein-Barr virus encoded small RNAs were detected by in situ hybridization. No monoclonal T-cell receptor gamma gene rearrangement was detected. Four weeks after surgery, the patient was treated with polychemotherapy and intrathecal methotrexate, but he died 2 months later.

Conclusions: This is the first report of a unique brain collision tumor consisting of a meningioma and an extranodal natural killer/T-cell lymphoma. Diagnosis depends on histopathology. Awareness of this entity is important to distinguish it from other intracranial tumors.