ABSTRACT
A 20-year-old man presenting with abdominal pain and distension from 3 months ago was admitted to our hospital. Colonoscopy showed a type 1 tumor in the transverse colon. The biopsy was moderately differentiated adenocarcinoma. Abdominal enhanced CT revealed intussusception associated with the tumor. After non-invasive reduction of intussusception was performed, a full-body examination revealed no findings suggestive of distant metastases or other Lynch syndrome- related tumors. We performed laparoscopic right hemicolectomy. Lynch syndrome was suspected based on his family history, MMR protein immunohistochemistry and MSI-High, but genetic testing was rejected due to cost reasons. If young people have chronic abdominal symptoms and a family history of suspected hereditary colorectal cancer, a close examination of colon cancer should be performed.