T cell malignant lymphoma in the central nervous system after acute lymphoblastic leukemia in a child.

A malignant lymphoma developed in the central nervous system (CNS) of a 7-year-old boy 5 years after he had received chemotherapy and cranial irradiation for acute lymphoblastic leukemia (ALL). Bone marrow analysis of the original leukemia showed a pre-B cell phenotype, whereas the resected brain tumor showed a T cell phenotype on immunophenotypic analysis. Because of this difference in immunophenotype, and because the patient had received multiple-drug chemotherapy and 1,800 cGy of cranial irradiation for the original ALL, we consider that the malignant lymphoma was a second neoplasm. This is a very rare case in two respects: it was a malignant lymphoma arising in the CNS as a second neoplasm after ALL and a T cell lymphoma occurring in a child.