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Background/Aims: To evaluate gastric early differentiate-type carcinogenesis, we attempted to identify clinicopathological and biological differences in differentiated-type minute intramucosal neoplasia (MIMN), which was defined as a tumor with a diameter of < 5 mm. Methods: We examined clinicopathological findings and biological factors, including TP53 overexpression, mucin phenotype, Ki-67-positive rate, MLH1, intranuclear accumulation of β-catenin, and DNA methylation status (low methylation epigenotype [LME], intermediate methylation epigenotype, and high methylation epigenotype [HME]) in MIMNs. In addition, non-MIMNs were also analyzed. In the present study, MIMN and non-MIMN were also examined based on low-grade dysplasia, high-grade dysplasia, and intramucosal cancer (IMC). Results: In clinicopathological findings, there were significant differences in sex ratios and tumor locations between MIMNs and non-MIMNs. Among the examined biological factors, no significant differences in the frequencies of biological factors were observed between the 2 intramucosal neoplasia types. However, the frequency of intranuclear accumulation of β-catenin was higher in non-MIMNs than in MIMNs. Finally, although the frequency of HME was significantly lower in MIMNs than in non-MIMNs, the opposite was observed for LME. Conclusions: The current finding suggested that DNA methylation and accumulation of β-catenin were closely associated with tumor development from MIMN to non-MIMN. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]