The ambiguity in the findings among several previous studies might be because of the difference in the age of the study population, yCRC and eCRC. The family history of CRC and cancer due to Crohn's disease or ulcerative colitis were also not excluded in such previous studies. Most importantly, those studies did not rule out the risk of hereditary cancer through the genetic testing in yCRC. Since hereditary CRC accounts for approximately 34% of those under the age of 35 years, it is necessary to exclude it to accurately compare the clinicopathological characteristics of sporadic cancer developed in yCRC and eCRC.
