Background: DOG1 is a calcium-dependent chloride channel encoded by the TMEM16A gene and is localized on chromosome 11q13. "DOG1 is expressed in cells of Cajal in the gastrointestinal tract, in acinar cells of the salivary gland (with apical membrane staining, especially serous cells), in acinar central cells of the pancreas, in hepatocytes, and in epithelial cells of the biliary tract, breast, stomach, and prostate." DOG1 is selectively expressed in gastrointestinal stromal tumors. Approximately 87% of gastrointestinal stromal tumors express DOG1. It is occasionally expressed in synovial sarcoma, leiomyosarcoma, etc.