PDGFRA and gastrointestinal stromal tumor: GIST display a wide variety of histopathological features, making it difficult to confirm with a definite diagnosis.[7] Pathologic diagnosis is based on both unique microscopic features (fusiform, epithelioid, or mixed type) and immunohistochemical techniques (CD117, CD34, actin, desmin, S-100, and Ki-67) with counting of the number of mitoses per 50 HPF.[18] Different types of mutations can be found in KIT and PDGFRA genes encoding a receptor tyrosine kinases type III (RTC).