[Two Cases Suspected of Lynch Syndrome Caused by Juvenile Rectal Cancer].

Case 1: A 28-year-old man was admitted to our hospital because of bloody stools that persisted for several months. Colonoscopy showed a 1/2 circumferential type 2 tumor in the rectum. Laparoscopic high anterior resection(D3)was performed for rectal cancer cT3N0M0, cStage Ⅱa. The final diagnosis was pStage Ⅱa, and MSI-high. XELOX therapy was performed for 3 months to prevent recurrence, and the patient is alive without recurrence. Case 2: A 51-year-old man, father of case 1 patient, was admitted to our hospital because of anemia and dyspnea. Colonoscopy showed a circumferential type 2 tumor in the ascending colon. Laparoscopic right hemicolectomy(D3)was performed for ascending colon cancer cT4b N2aM0, cStage Ⅲc. The final diagnosis was pT3N0M0, pStage Ⅱa, and MSI-high. The patient is alive no recurrence without adjuvant chemotherapy. Both patients had a family history of colorectal cancer, were MSI-high, met the Amsterdam criteria Ⅱ and the revised Bethesda guidelines, and were suspected of having Lynch syndrome. A detailed family history and appropriate information provision were considered useful.