Neurofibromatosis type 1 and childhood cancer.

BACKGROUND: Patients with neurofibromatosis type 1 (NF1) are prone to develop malignancy, particularly malignant schwannoma and glioma in adults.
METHODS: To assess the risk for childhood malignancy in NF1, 26,084 patients with cancer younger than 15 years of age registered from 1969 to 1989 in the Japan Children's Cancer Registry were reviewed. The incidence of NF1 in each type of cancer was compared with that in the Japanese population.
RESULTS: Fifty-six children with cancer had NF1 in the national registry. The incidence of NF1 (0.21%) was 6.45 times that of the expected estimated rate of 1 per 3000 in the Japanese population. These tumors tended to be type and site specific. The NF1 incidence was extremely high in optical nerve glioma (12.5%), other central nervous system gliomas (0.9%), and malignant schwannoma (31.4%). For nonneural tumors, NF1 incidence was increased in rhabdomyosarcoma (1.36%), particularly those in urogenital organs, and in myelogenous leukemia (0.27%). Epithelial carcinomas were not observed in the group of patients with NF1.
CONCLUSION: The risk for glioma and malignant schwannoma increases in children and adults with NF1. Moreover, the risk for two childhood malignancies, myelogenous leukemia and rhabdomyosarcoma, increases in children with NF1. The NF1 gene seems to increase the risk not only for neural tumors but also for some non-neural tumors in an age-specific, organ-dependent pattern of carcinogenesis.