RESUMEN
Gastrointestinal stromal tumor [GIST] is a new distinct entity defined as CD117 or c-kit positive mesenchymal tumors, originaling in gastrointestinal pacemaker cells known as interstitial cells of Cajal. This study evaluate the percentage of GIST previously diagnosed as mesenchymal tumors in our hospital during 11 years. A total of 30 surgically resected gastrointestinal tumor specimens were collected from January 1990 to December 2000 in the pathology laboratory of La Rabta Jospital. Immunohistochemical studies were performed on these tumors with antibodies of CDI 17, smooth muscle actin [SMA] and protein S-100. Among the 30 tumors, 26 [86.6%] were CD117 positive and were classified as gastrointestinal stromal tumors. Among the 26 GIST, SMA was positive in 11 tumors [42.3%], 6 tumors [23%] expressed protein S- 100. The 4 tumors classified as non-GIST were leiomyomas with the following immunohistochemical characteristics: CD117-negative with strong SMA-positive and protein S100 negative status. The majority [86.6%] of mesenchymal gastrointestinal tumors were GIST, except for a smalls groups of smooth muscle tumors