Do colon cancers randomly occur anywhere in the colon, or are they concentrated in the part closest to the rectum?

More common distal. The most common site for colon cancer to appear is in the rectosigmoid colon, the end of the colon nearest to the rectum. If you are 50 or older, be sure to get a colonoscopy to screen for colon cancer.
Colon cancer. Colon cancer can occur randomly in any part of the bowel. Cancers on the left side of the colon are more common (70%) with about 30% occurring on the right side.
Any place. Colon cancers can occur anywhere in the colon, but statistically in the us colon cancers do occur more often in the left side of the colon or sigmoid colon region.