Symptoms:

Many cases of colon cancer have no symptoms. The following symptoms, however, may indicate colon cancer:

• Abdominal pain and tenderness in the lower abdomen
• Blood in the stool
• Diarrhea, constipation, or other change in bowel habits
• Narrow stools
• Weight loss with no known reason

Signs and tests:

With proper screening, colon cancer can be detected before symptoms develop, when it is most curable.

Your doctor will perform a physical exam and press on your belly area. The physical exam rarely shows any problems, although the doctor may feel a lump (mass) in the abdomen. A rectal exam may reveal a mass in patients with rectal cancer, but not colon cancer.

A fecal occult blood test (FOBT) may detect small amounts of blood in the stool, which could suggest colon cancer. However, this test is often negative in patients with colon cancer. For this reason, a FOBT must be done along with colonoscopy or sigmoidoscopy. It is also important to note that a positive FOBT doesn't necessarily mean you have cancer.

Imaging tests to screen for and potentially diagnose colorectal cancer include:

• Colonoscopy
• Sigmoidoscopy

Note: Only colonoscopy can see the entire colon, and this is the best screening test for colon cancer.

Blood tests that may be done include:

• Complete blood count (CBC) to check for anemia
• Liver function tests

If your doctor learns that you do have colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest, or brain may be used to stage the cancer. Sometimes, PET scans are also used.

Stages of colon cancer are:

• Stage 0: Very early cancer on the innermost layer of the intestine
• Stage I: Cancer is in the inner layers of the colon
• Stage II: Cancer has spread through the muscle wall of the colon
• Stage III: Cancer has spread to the lymph nodes
• Stage IV: Cancer has spread to other organs

Blood tests to detect tumor markers, including carcinoembryonic antigen (CEA) and CA 19-9, may help your physician follow you during and after treatment.