BACKGROUND AND STUDY AIMS: The diagnosis and surveillance of gastrointestinal stromal tumor (GIST) rely on pathology and immunochemistry (IHC), making it complicated and invasive. Noninvasive and convenient biomarkers of this disease need to be explored. The high specificity and sensitivity of IHC in detecting GIST 1 (DOG1) in biopsy indicate that it is also expressed in circulating tumor cells of the blood and may be an ideal biomarker for GIST. This aimed to detect the expression of DOG1 in peripheral blood cells (PBCs) and determine the relationship between DOG1 expression and clinical factors. PATIENTS AND METHODS: A total of 45 patients with GIST and 46 healthy controls (HCs) were recruited from the Second Affiliated Hospital of Nanchang University between December 2015 and June 2018. PBCs were isolated from peripheral venous blood by density gradient centrifugation. RNA was extracted from PBCs, and DOG1 mRNA was detected by quantitative reverse transcription polymerase chain reaction. DOG1 mRNA expression between GIST and HC was compared, and the relationship between clinical factors and DOG1 was also analyzed. RESULTS: DOG1 mRNA expression in PBCs was significantly higher in patients with GIST than that in HCs (3.326 [1.942-5.328] versus 0.744 [0.269-1.087], p < 0.01). The specificity and sensitivity were 88.9% and 89.1%, respectively (AUC = 0.912). Tumor diameter and risk of aggressive behavior were correlated with DOG1 expression, and other clinical factors (sex, age, location, number of phase-splitting cells, Ki-67 index, metastatic status) did not show any relationship with DOG1 expression. However, clinical factors, including tumor diameter and risk grade, were not independent factors in DOG1 expression when multivariate analysis was conducted. CONCLUSION: DOG1 expressions were significantly higher in patients with GIST than that in HCs. Tumor diameter and risk classification correlated with DOG1 expression but were not independent factors. DOG1 in PBCs is a promising noninvasive biomarker for GIST.