Tissue diagnosis necessary for small endoscopic ultrasound‐suspected gastric gastrointestinal stromal tumors 2 cm or less in size: A prospective study focusing on the endoscopic incisional biopsy

Background and Aim The small endoscopic ultrasound (EUS)‐suspected gastric gastrointestinal stromal tumors (GISTs), gastric subepithelial tumors at the muscularis propria layer on EUS, are detected frequently. Bite‐on‐bite forceps biopsy and EUS‐guided tissue sampling yield variable results. This study aimed to analyze clinicopathologic features of the small EUS‐suspected gastric GISTs 2 cm or less in size and to evaluate the efficacy and safety of the endoscopic incisional biopsy (EIB) for these small tumors. Methods This prospective study investigated 70 patients with small EUS‐suspected gastric GISTs 2 cm or less in size in two stages. Firstly, 30 patients were recruited for the efficacy and safety evaluation of the EIB. Secondly, 40 patients were randomly assigned to receive either EIB or the bite‐on‐bite biopsy for comparison of the diagnostic yield, procedure time, and adverse event rate. Results Combining two study stages, leiomyoma (74%) was diagnosed histologically to outnumber GIST (26%) with a diagnostic rate of 94% for patients receiving EIB. KIT exon 11 mutations (50%) and PDGFRA exon 12 mutations (16%) were detected in the small gastric GISTs. In the direct comparison, the diagnostic yield of EIB and the bite‐on‐bite biopsy was 85% and 50%, respectively (P = 0.018). There was no statistically significant difference of the mean procedure time or adverse event rate between these two groups. Conclusions Leiomyoma is more common than expected among these small tumors. Tissue diagnosis with an effective and safe sampling technique, such as EIB, is necessary for making further clinical decisions.