ANO1 and atrial fibrillation: GIST typically show positive expression for CD34, CD117, and DOG-1, while duodenum-derived AF is negative for these markers.[3] In this case, the postoperative pathology showed that the tumor cells were negative for CD34, CD117, DOG-1, S-100, SOX-10, and H3K27M, which confirmed the diagnosis of duodenum-derived AF (Fig. 3).