Razi Journal of Medical Sciences

    Background & Aim: Gastrointestinal stromal tumors(GISTs) are the most common mesenchymal tumors of gastrointestinal tract. They are known to express c-kit, which is important in their diagnosis and treatment. The aim of our study was to assess the morphologic and immunohistochemical features of gastrointestinal stromal tumors and the significance of c-kit expression in them. Materials and Methods: The study was descriptive and simple method for sampling was used. Files from pathology laboratory of National Iranian Blood Transfusion Organization were searched for cases referred as GIST between April 2002 and April 2005. Clinical data were recorded and their H&E and IHC slides studied. The results were analyzed by SPSS 10 software. Results: C-kit expression is a key confirmatory marker for GIST diagnosis. Therefore out of 31 referred cases only 22 cases of GISTs(12 males, 10 females) were included in this study. The patient's median age was 51 years. GISTs most frequently occurred in the stomach(12 cases) followed by small intestine(9 cases) and colon(1 case). The size of tumors ranged from 2.5 to 15 cm. Also 72.7% of tumors were hypercellular. Benign spindle cell tumors were 31%, malignant spindle cell tumors 23%, benign epithelioid tumors 23% and malignant epithelioid tumors constituted 23%. Mucosal invasion and tumoral necrosis were present in 22.7% and 27% of cases, respectively: 72.8% of tumors had mitotic activity exceeding 5 per 50 hpf. The expression of other IHC markers were: Vimentin 63.1%, Desmin 13.1%, Smooth muscle actin 22.7%, S-100 protein 22.7% and CD34 63.6%. Conclusion: With regard to the crucial role of c-kit in the pathogenesis of GISTs, c-kit expression is essential for their diagnosis and therapy therefore, tumors which are negative for c-kit, especially those with spindle fascicles, most probably are other mesenchymal neoplasms such as leiomyomas, schwannomas, etc., and should be classified according to their IHC markers. Long-term follow up of all GISTs patients is recommended.