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Background/Aims: The prevalence of Helicobacter pylori-naive status is increasing. Nonetheless, biennial gastroscopy is recommended for all Koreans aged 40 to 75 years. This study aimed to determine whether gastric cancer screening guidelines could be changed according to H. pylori infection status and year of birth. Methods: Koreans who underwent serum assays and gastroscopy for gastric cancer screening between 2010 and 2016 were included if screening tests were followed up for ≥3 times. H. pylori infection was confirmed when invasive tests or 13C-urea breath tests were positive. In the case of negative test findings, eradication history, serologically detected atrophy, and intestinal metaplasia/atrophy were checked for past infection. If all were absent, H. pylori-naive status was confirmed. Results: Two-thousand and two (256 H. pylori-naive, 743 past-infected, and 1,003 infected) Koreans underwent screening tests for 95.5±28.4 months. The mean year of birth in the naive group (1969±7) differed from those of the past-infected (1957±10, p<0.001) and infected (1958±10, p<0.001) groups. H. pylori-naive status was correlated with recent year of birth (r=0.368, p<0.001). No gastric tumors were observed among the naive participants (p=0.007), whereas 23 adenomas, 18 adenocarcinomas, and two neuroendocrine tumors were detected in 1.9% (14/743) of past-infected and 2.5% (25/1,003) of infected participants, including four infected participants with metachronous tumors. Conclusions: The prevalence of H. pylori-naive status is increasing in young Koreans, and gastric tumors are rare in this population. Hence, biennial gastroscopy could be waived after the confirmation of naive status. [ABSTRACT FROM AUTHOR]

Background/Aims: The presence of invasion is a diagnostic criterion of early gastric cancer (EGC) in Korea, whereas diagnosis in Japan is based on enlarged nuclei and prominent nucleoli. Moreover, the depth of invasion is the location of cancer cell infiltration in Korea, whereas it is the location of lymphovascular invasion (LVI) or cancer cell infiltration in Japan. We evaluated the characteristics of EGC with LVI to uncover the effects of different diagnostic criteria. Methods: Consecutive T1-stage EGC patients who underwent complete resection were included after endoscopic or surgical resection. The presence of LVI was evaluated. Results: LVI was present in 112 of 1,089 T1-stage EGC patients. LVI was associated with depth of invasion (p<0.001) and age (p=0.017). The prevalence of LVI in mucosal cancer was significantly higher in Korea (p<0.001), whereas that of submucosal cancer was higher in Japan (p=0.024). For mucosal EGC types, LVI was positively correlated with diagnostic criteria applied in Korea (p=0.017). For submucosal EGC types, LVI was positively correlated with Japanese criteria (p=0.001) and old age (p=0.045). Conclusions: The higher prevalence of LVI for mucosal EGC in Korea and for submucosal EGC in Japan indicates that different diagnostic criteria should be considered when reading publications from other countries. [ABSTRACT FROM AUTHOR]

Background/Aims: Microsatellite instability (MSI) plays a crucial role in gastrointestinal carcinogenesis. The aim of this study was to clarify whether MSI is a useful marker for predicting synchronous gastric and colorectal neoplasms. Methods: Consecutive patients who underwent both esophagogastroduodenoscopy and colonoscopy before the resection of gastric or colorectal cancers were included. MSI was analyzed using two mononucleotide and three dinucleotide markers. Results: In total, 434 gastric cancers (372 microsatellite stability [MSS], 21 low incidence of MSI [MSI-L], and 41 high incidence of MSI [MSI-H]) and 162 colorectal cancers (138 MSS, 9 MSI-L, and 15 MSI-H) were included. Patients with MSI gastric cancer had a higher prevalence of synchronous colorectal cancer, colorectal adenoma, and gastric adenoma than those with MSS gastric cancers (4.8% vs 0.5%, p=0.023; 11.3% vs 3.2%, p=0.011; 3.2% vs 1.2%, p=0.00, respectively). The prevalence of synchronous colorectal adenomas was highest in MSI-L gastric cancers (19.0%), compared with MSI-H (7.3%) or MSS (3.2%) gastric cancers (p=0.002). In addition, there were no significant differences in the prevalence rates of synchronous colorectal adenoma among the MSI-H (13.3%), MSI-L (11.1%), and MSS (12.3%) colorectal cancers (p=0.987). Conclusions: The presence of MSI in gastric cancer may be a predictor of synchronous gastric and colorectal neoplasms, whereas MSI in colorectal cancer is not a predictor of synchronous colorectal adenoma. [ABSTRACT FROM AUTHOR]