Anorectal Cancer

The anal canal is a narrow tube surrounded by a muscle at the end of the rectum. The rectum is the lower part of the colon (large intestine). If you undergo a bowel movement, the poop exits the body into the anal canal from the rectum. Cancer starts as certain cells of the body differentiate without stopping. As cancer spreads, it can linger in surrounding tissues or spread to other areas of the body, a phenomenon called metastases. Anal cancer starts in the cells near or just beyond the opening of the anal.