[Insights on colorectal carcinoma based on the biological differences between left-sided and right- sided colon cancers].

Previous studies have demonstrated that there are biological differences between colon and rectal cancers. Recently, some authors have proposed that colorectal cancer could be classified into several categories according to the primary sites of the tumor, proximal or distal. It is speculated that the differences are due to different embryologic origin and time to initial diagnosis. Further evidence supports that the molecular differences in the status of K-ras, BRAF, and microsatellite instability (MSI) based on primary sites in the bowel are the basis that impacts the response to therapeutic agents and patient prognosis.