Gastrointestinal Stromal Tumors associated with Neurofibromatosis Type I: A Report of Two Cases

ABSTRACT

Gastrointestinal stromal tumor (GIST) is the most common non-epithelial neoplasm arising in the gastrointestinal tract, but this tumor is rarely seen in association with type 1 neurofibromatosis (NF-1). We report here on two cases of multiple GISTs of the small intestine that occurred in NF-1 patients. We also analyzed the mutations of c-kit exons 9, 11, 13 and 17 and the plateletderived growth factor receptor-alpha (PDGFRA) exons 12 and 18 in two GIST patients. Histologically, the NF-1-associated GISTs were similar to those of non-the NF-1 GISTs, but they characteristically revealed hyperplastic interstitial cells of Cajal around the GISTs. Immunohistochemically, these tumors showed strong co-expressions of CD117 and CD34. The molecular genetic analysis of the GISTs showed that all of the c-kit and PDGFRA exons that were analyzed in the GISTs of the two patients were the wild-type, suggesting a limited role for the c-kit and PDGFRA mutations in the tumorigenesis of NF-1-associated GISTs.