Gastrointestinal stromal tumors in Japanese patients with neurofibromatosis type I

Neurofibromatosis type I (NF1) predisposes patients to various neoplasias, including gastrointestinal stromal tumors (GISTs). Little is known about the risk of developing GISTs for NF1 patients or the clinicopathologic features and prognosis of NF1-GIST. We conducted a multi-detector computed tomography screen for adult NF1 patients between 2003 and 2012. Clinicopathologic data of sporadic GISTs from patients who underwent surgery between 2001 and 2010 were retrospectively collected from 32 hospitals in Japan. CT screening identified 6 GIST patients from the 95 NF1 patients screened, suggesting that the prevalence rate of GISTs was approximately 6.3/100 in NF1 patients. All 6 NF1 patients exhibited hyperplasia of the interstitial cells of Cajal in the adjoining small intestine. NF1-GISTs may account for 1.1-1.3 % of primary sporadic GISTs and present as multiple tumors in the small intestine, with low mitotic activity and no KIT or PDGFRA mutations. The risk of recurrence and mortality is very similar between NF1 and non-NF1 patients after surgical resection of GISTs. NF1 patients may be predisposed to developing small intestinal GISTs, which may appear as multiple GISTs without KIT and PDGFRA mutations. The prognosis of patients with NF1-GISTs is similar to patients with conventional GISTs.