GISTs are, finally, defined as pleomorphic mesenchymal tumors of the GI tract that express the KIT protein (CD 117- Protooncogene that encodes the transmembrane tyrosine kinase receptor CD 117 detected by flow cytometry in most cases of acute myeloid leukemia, in small numbers of T- and B-lymphoblastic lymphomas, and in some gastrointestinal stromal tumors - stem cell factor receptor) and often also CD34 (human progenitor cell antigen) on immunohistochemistry [6]. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.