To screen Lynch syndrome (LS), family history taking is an important element. However, in the patient of early colorectal cancer who could be treated by endoscopically procedures, generally endoscopists do not enough list medical history or detailed family history. Herein we report a 60-year-old woman who suspected LS by her family history before treatment and genetic testing. She was referred to our hospital to receive treatment for rectal cancer diagnosed at a local clinic. After our precise family history taking, we found that her family history was fulfilled both the Amsterdam criteria II and revised Bethesda guidelines. Curative resection was performed by endoscopic submucosal dissection, and the lesion was diagnosed as a carcinoma in situ. After genetic counseling, she agreed with analyses for germline mutations and then we found a pathogenic variant in the mismatch repair gene, MSH2. The case we experienced tell us that clinicians, especially endoscopists, had better pay more attention to family history taking.
