Endoscopic features of gastric neuroendocrine carcinoma

Abstract Background and Aim The endoscopic features of gastric neuroendocrine carcinoma (G‐NEC) have not been clarified; therefore, they were investigated in relation to clinicopathological findings. Methods Consecutive patients with G‐NECs who had undergone endoscopic or surgical resection at our institution between January 2005 and March 2022 were included in this retrospective study. The endoscopic and clinicopathological findings of the lesions were analyzed to provide information of diagnostic value. In addition, cases of gastric neuroendocrine tumor (G‐NET) and common‐type gastric adenocarcinoma treated in the same study period were identified to compare the endoscopic findings between each G‐NEC versus G‐NET, and G‐NEC versus common‐type gastric adenocarcinoma. Patients with common‐type gastric adenocarcinoma were matched for age, sex, tumor size, and depth of tumor invasion in 1:3 ratio. Results Among 15 patients with 15 G‐NECs, submucosal tumor‐like marginal elevation (87%), adherent white coat (67%), and ulceration with a distinct border (60%) were characteristic endoscopic findings in white‐light images. Magnifying narrow‐band imaging endoscopy revealed an absent microsurface (MS) pattern plus disrupted irregular microvessel (MV) in five (71%) of seven cases with evaluable MS and MV patterns. The area with an absent MS pattern plus disrupted irregular MV corresponded to the histological finding of NEC component in all five cases. These endoscopic features were all significantly more frequent in G‐NECs than G‐NETs ( n = 22) or common‐type gastric adenocarcinomas ( n = 45). Conclusions These endoscopic features should be taken into consideration to increase the index of suspicion and to improve the accuracy of target biopsies for G‐NEC.