ANO1 and gastrointestinal stromal tumor: GIST typically show positive expression for CD34, CD117, and DOG-1, while duodenum-derived AF is negative for these markers.[7] In this case, the postoperative pathology showed that the tumor cells were negative for CD34, CD117, DOG-1, S-100, and Desmin, which confirmed the diagnosis of duodenum-derived AF.