Gastrointestinal stromal tumors (GISTs) constitute the majority of gastrointestinal mesenchymal tumors, characterized by the expression of a proto-oncogene protein, CD117, which is detected by immunohistochemistry.[13] The identification of mutations in exon 11 and also exons 9 and 13 of the c-kit proto-oncogene coding for c-kit (CD117) in majority of GISTs resulted in a better understanding of their oncogenic mechanisms. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.