Clinical and Pathological Challenges in the Diagnosis of Gastric-Type Differentiated Adenocarcinoma in the Stomach: A Study of Endoscopic Submucosal Dissection Cases

Background/Aims: Gastric-type differentiated adenocarcinoma (GDA) of the stomach is a rare variant of gastric cancer that is highly infiltrating and exhibits early metastasis. However, the endoscopic and pathological features of “early-stage” GDA remain unknown. The aim of this study is to characterize early-stage GDA. Methods: We retrospectively enrolled 479 differentiated-type early gastric cancer cases who underwent endoscopic submucosal dissection (ESD). GDA cases were selected based on morphology and immunohistochemistry. Clinicopathological data were compared between gastric- and intestinal-type differentiated adenocarcinomas (IDAs). Results: Thirteen lesions were classified as GDAs. GDAs as well as IDAs showed irregular microvascular and microsurface patterns with clear demarcation line on magnifying endoscopy with narrow band imaging (M-NBI). The rate of pathological misdiagnosis of GDAs in biopsy specimens was higher than that of IDAs ( p = 0.016). GDA was significantly associated with positive lymphovascular invasion ( p = 0.016). There was one intramucosal lesion with lymphatic invasion in GDA. Conclusions: Although M-NBI is useful to detect GDA, the pathological diagnosis of GDAs in biopsy specimens often remains challenging. When suspicious lesions are not diagnosed as GDA, they should be followed up intensively, or diagnostic ESD has to be performed. ESD specimens should be carefully evaluated because of a higher incidence of lymphovascular invasion.