HISTOPATHOLOGICAL CHARACTERISTICS AND IMMUNOCHEMICAL EXPRESSING IN EXTRAGASTROINTESTINAL STROMAL TUMORS

Abstract

Background: Extragastrointestinal stromal tumors (EGISTs) are gastrointestinal stromal tumors(GISTs) that located in abdomen but outside the gastrointestinal tract. EGISTs is not common as GISTs with rate of 1-5%. Previously, EGISTs often diagnosed as gastrointestinal smooth muscle tumors, fibrous tumor or schwannomas. After the presence of the c-kit selective therapy administration(specified inhabition of CD117), the same as GIST, the EGIST are well responsed to this therapy, even when the tumors are at late stages such as invasion or metastasis. . Up to now immunohistochemistry has been indispensable for the diagnosis of EGIST in addition to the standard histopathology. Objectives: To classify the mesenchymal tumors in the abdomen outside the gastrointestinal tract. To study the Histopathological characteristics and Immunohistochemistrical expressing in EGIST. Materials and methods: discriptive research of 14 mesenchymal tumors in the abdomen outside the gastrointestianl tract. Using the inside and outside control for the immunohistochemistrical assessment. Results: 8/14 (57,1%) of these were GISTs, following the leiomyomas and leiomyosarcomas (21,3%). The others are less common including Schwannomas, fibromatosis and lipoma. The EGIST size: 10cm to 35cm, the average 19cm. The fusiform EGISTs accounting for 75%, the other types are less common, encompassing epithelioid and mixed tumors. Risk of Aggressive Behavior in EGIST: the high risk encompassing 100%. The positive proportion of the immunochemistrical markers: CD117 (100%), CD34 (62,5%), SMA (25%), S100 (12,5%). Desmin and CK negative in all cases.