Neurofibromatosis type 1, gastrointestinal stromal tumor, leiomyosarcoma and osteosarcoma: four cases of rare tumors and a review of the literature.

Background: Neurofibromatosis type 1 (NF1) is a genetic syndrome that predisposes patients to benign and malignant tumor development. Patients with NF1 develop multiple neurofibromas that can transform into aggressive sarcomas known as malignant peripheral nerve sheath tumors. In contrast, malignant tumors unrelated to the nervous system rarely coexist with neurofibromatosis.