In our study, initial immunohistochemical study of liver and pancreas specimens showed CD117 (+), while that of liver biopsy and peritoneal specimens at second- surgery detected CD117 (-) and SMA(+), which is indicative of transformation of extra-gastrointestinal stromal tumors to primary pancreatic leiomyosarcoma. This evidence concerns the gene SMN1 and gastrointestinal stromal tumor.