[A case of extragastric pedunculated gastrointestinal stromal tumor of the stomach with peritoneal dissemination].

Here, we present the case of a 73-year-old woman in whom abdominal computed tomography showed an abdominal tumor (13 cm in diameter) in the backspace of the posterior gastric wall. Its feeding artery was detected to be the left gastric artery by abdominal angiography. We diagnosed it as a gastrointestinal stromal tumor (GIST) of the stomach and performed an operation. Peritoneal dissemination was observed and the tumor was connected to the gastric wall by a stalk. Histologically, the tumor consisted of spindle-shaped cells. Immunohistochemical staining showed positive c-kit and CD34 expression and negative SMA and S100 protein expression. Therefore, we diagnosed this as a case of extragastric pedunculated GIST of the stomach with peritoneal dissemination. After surgery, internal use of imatinib was started. The patient is still followed up 15 months after the operation. Combination therapy of tumor resection and imatinib chemotherapy might improve the prognosis of patients with GIST of the stomach with pedunculated growth.