[Gastrointestinal stromal tumors in neurofibromatosis type 1]

Neurofibromatosis type 1 or Recklinghausen disease is one of the most common hereditary autosomal dominant diseases. The disease-causing gene can be found on chromosome 17 as an NF1 tumor suppressor gene. The mutation of this gene leads to the loss of tumor suppressor function, which in turn causes the development of benign and malignant tumors. In 25% of the cases gastrointestinal manifestations are found, most often GIST. The close correlation of the two diseases are well known in the literature, there are more than 160 published cases. GIST develops in 7% of patients with neurofibromatosis, and among these patients the occurrence of NF1 is 150-180 times more frequent than in the general population. Neurofibromatosis associated with GIST is a different entity and, unlike sporadic GIST, it is usually multiplex and almost always develops in the small bowel. There is a slightly higher incidence among women than in men, and the disease develops at young age. Histological characteristics include spindle cell type, skeinoid fibers and frequent S100 positivity. Low mitotic activity usually suggests better prognosis. c-KIT and PDGFRA mutation is very rare, in agreement with the hypothesis that the pathogenesis of NF1-GIST is not c-KIT dependent. It is presumed that neurofibromatosis associated and sporadic GIST have different pathogenesis, and that the development of GIST tumor in neurofibromatosis is part of the hereditary disease. c-KIT and PDGFRA mutations--as shown in a few known cases--probably develop at a later step of tumor genesis. Imatinib, which has revolutionized the therapy of GIST, cannot be used in this patient group, however, as of today not enough information is available.