Primary malignant lymphoma of the central nervous system in an immunocompetent child: a case report.

Primary lymphoma of the central nervous system (PCNSL) is extremely rare, especially in childhood. A 9-year-old Japanese boy was diagnosed as having precursor-B cell-type lymphoblastic lymphoma, based on morphologic and immunocytochemical analysis of mononuclear cells in the cerebrospinal fluid and a positive reaction for terminal deoxynucleotidyl transferase (TdT), CD19, CD79a, and CD179b. After seven courses of chemotherapy and craniospinal radiotherapy, the patient is alive, well, and in continuous complete remission. Despite its rarity, PCNSL should be included in the differential diagnosis in the presence of symptoms of increased intracranial pressure and/or unusual imaging findings of the brain.