[A case of gastric cancer developed after pylorus-preserving gastrectomy in a patient with lynch syndrome].

Lynch syndrome is an inherited autosomal dominant disorder caused by germ-line mutation of mismatch repair genes, in which a malignant tumor develops at a young age in the colon, endometrium, stomach, or other tissues. A 54-year-old patient with gastric cancer received pylorus-preserving gastrectomy, and a genetic examination confirmed a pathological variation of the MLH1 gene. Five years after surgery, an upper gastrointestinal endoscopy revealed a residual 0 -IIa+IIc gastric tumor approximately 2 cm in size extending from the anastomotic site to the lesser curvature side of the stomach. The remaining stomach was completely removed. The final diagnosis was T1b (SM) N1M0, StageIB gastric cancer. Microsatellite instability was positive, and we attributed the cancer to Lynch syndrome. In Lynch syndrome, the risk of multicentric gastric cancer is higher than normal, and for the initial therapy, preventive total gastrectomy should be considered as an option.