Although blood in the stool is one of the more common signs of colorectal cancer, other symptoms can occur depending on the cancer's specific location. Many patients are free of signs or symptoms until their tumors are quite advanced. Blood found in the stools is a common sign of many intestinal cancers. Blood in the stool may appear red if it is fresh, or black if it is old. Although it should be reported to a physician immediately, this sign is often caused by conditions other than cancer, including hemorrhoids, minor tears around the rectal or anal areas, or diverticulosis.
Stools can turn red after eating certain red foods, such as beets or red licorice.
Iron supplements and medications that have bismuth subsalicylate, most commonly Pepto-Bismol, can cause stools to turn black. Weight loss and changes in bowel movements are also general symptoms for colon cancer. Symptoms of Cancers in Specific Areas of the Colon Symptoms of colorectal cancer vary widely depending on the location of the cancer within the large intestine. The waste matter in the first portion of the colon is in liquid or semi-liquid form. Tumors that develop here do not change bowel habits or stool formation.