A collision tumor: Primary central nervous system B-cell lymphoma and anaplastic astrocytoma

A collision tumor in the central nervous system (CNS) is a rare entity. We report a case of a collision tumor with primary CNS lymphoma and astrocytoma in an otherwise healthy young male and the diagnostic challenge associated with it. The tumor showed 2 histologic patterns. The predominant component consisted of anaplastic astrocytoma with gemistocytic appearance, and the lymphoma cells were kappa restricted B cells with variable cell sizes and some plasmacytoid differentiation. In situ hybridization demonstrated that the lymphoma cells were Epstein-Barr virus (EBV) positive. The patient was neurologically asymptomatic for 2 and half years following surgery, chemotherapy, and radiation.