Natural History of Exophytic Type Gastrointestinal Stromal Tumor: A Case Report

: Gastrointestinal stromal tumor (GIST) is the most common submucosal tumor of the stomach. GISTs are often detected by esophagogastroduodenal endoscopy. We have previously reported on endoscopically invisible medium-sized exophytic type GISTs. We present here a case of small exophytic GIST detected by transabdominal ultrasonography (TUS) in which the natural history of the tumor could be traced retrospectively through incidental findings obtained during follow-up for intraductal papillary mucinous neoplasm by magnetic resonance of imaging or computed tomography over about 10 years. The tumor appeared 7 years before its detection, and the doubling time was calculated as 6.9 years. In conclusion, low-risk exophytic GIST was estimated to have taken at least about 7 years to reach a size detectable by TUS.