[A case report of huge abdominal recurrent tumor of small intestinal GIST after 15 years from the operation with primary lesion].

A man in his 60s was given an emergency operation 15 years ago for abdominal bleeding. His tumor of small intestine was resected and diagnosed as small intestinal leiomyosarcoma. He came to our hospital because of his abdominal masses 15 years after the initial operation. CT scan showed a 15 cm-sized solid and cystic tumor in the pelvic cavity. The tumor was diagnosed as GIST by PET-CT and MRI. The tumor was resected, and pathological findings led to the diagnosis of GIST with this tumor. Previous tumor cells were slightly-positive for kit immunohistological examination, but did not resemble this tumor cells morphologically. So genetic tests were performed and revealed two tumors had same mutations of c- kit. Finally, we could diagnose the tumor was recurrent metastases of small intestinal GIST 15 years after the initial surgery. kit mutation analysis was useful for a diagnosis of recurrences and predictions of the clinical response to imatinib in GISTs.