GISTAppendix

Note 1: Most gastrointestinal stromal tumors (GISTs) have oncogenic mutations of the KIT gene, which is located on chromosome 4q. KIT is a cytokine receptor which binds to stem cell factor, which causes certain types of cells to grow; altered forms of KIT may be associated with some types of cancer. This test detects expression of the KIT gene in tumor tissue sections using immunohistochemical (IHC) stains. Test results are available in the pathology report. A positive test helps to establish the diagnosis of GIST and to identify patients for whom treatment with agents such as imatinib mesylate (Gleevec) or sunitinib malate (Sutent) is appropriate. Do not record secondary or acquired mutations that may have developed because of long-term imatinib treatment.
Note 2: Another name for KIT is CD117.
Note 3: See CS Site-Specific Factor 13 for coding information about specific mutations of the KIT gene detectable with molecular testing. See CS Site-Specific Factor 14 for coding information about mutations of the PDGFRA gene.

Code	Description
010	Positive/elevated
020	Negative/normal; within normal limits
030	Borderline; undetermined whether positive or negative
988	Not applicable: Information not collected for this case (If this information is required by your standard setter, use of code 988 may result in an edit error.)
997	Test ordered, results not in chart; results pending
998	Test not done (test not ordered and not performed)
999	Unknown or no information Not documented in patient record

CS Site-Specific Factor 12KIT Gene Immunohistochemistry (IHC)