Gastrointestinal Stromal Tumor.

Abstract Gastrointestinal stromal tumour is the most common mesenchymal tumour of the human gastrointestinal tract. The c-kit receptor tyrosine Kinase is expressed by practically all GIST. Interstitial cells of Cajal are the pacemaker of the peristaltic movement of the G.I. tract and these tumors are considered to originate from this cells. A great majority of them occurs in the stomach (60-70%) and small intestine (25% to 35%). Some GIST are primary in the omentun, mesentery of retroperitoneum. Although the prediction of malignancy in this tumour group is notorious by difficult, tumors that have mitotic activity count, exceeding 5 per 50 HPF of those larger than 5 cm have a high frequency of intra-abdominal recurrence and liver metastasis. Functional analysis of the different c-kit mutations and their impact on the response to tyrosine Kinase inhibitor are under intense investigation.