A rare case of extraluminally pedunculated gastrointestinal stromal tumor with postoperative metastasis to pancreas

The gastrointestinal stromal tumor (GIST) is the most common type of sarcomatous tumor of the gastrointestinal tract. Many GISTs appear as submucosal tumors with intraluminal protrusion. GISTs with malignant features have a high risk of postoperative recurrence or metastasis, usually to the liver or peritoneum. We present a case of gastric GIST with double rarities: arising completely extraluminally with a pedicle and postoperative metastasis to the pancreas. A woman in her seventies diagnosed with a large extraluminal gastric GIST underwent complete removal of the tumor. Nine months later, a solitary metastatic tumor in the pancreas was detected. Imatinib controlled metastasis well for four years before the tumor became resistant. The patient then had a partial pancreatectomy with splenectomy. She is currently free from recurrence. We genetically analyzed the primary and metastatic GISTs and found known mutations related to poor prognosis and imatinib resistance.