Colon Cancer

Diagnosis & Staging

If a person has any signs or symptoms of colon cancer, the doctor must determine whether they are due to a diagnosis of colon cancer or some other cause. The doctor asks about personal and family medical history and may do a physical exam.

If the physical exam and test results do not suggest the presence of colon cancer, the doctor may decide that no further tests are needed and no treatment is necessary. However, the doctor may recommend a schedule for checkups.

If tests show an abnormal area (such as a polyp), a biopsy to check for cancer cells may be necessary. Often, the abnormal tissue can be removed during colonoscopy or sigmoidoscopy. A pathologist checks the tissue for cancer cells using a microscope.

To help find the cause of symptoms, the doctor evaluates a person's medical history. The doctor also performs a physical exam and may order one or more diagnostic tests.

  • X-rays of the large intestine, such as the DCBE, can reveal polyps or other changes.

  • A sigmoidoscopy lets the doctor see inside the rectum and the lower colon and remove polyps or other abnormal tissue for examination under a microscope.

  • A colonoscopy lets the doctor see inside the rectum and the entire colon and remove polyps or other abnormal tissue for examination under a microscope.

  • A polypectomy is the removal of a polyp during a sigmoidoscopy or colonoscopy.

  • A biopsy is the removal of a tissue sample for examination under a microscope by a pathologist to make a diagnosis.

Stages of Colorectal Cancer

If the diagnosis is colon cancer, the doctor needs to learn the stage (or extent) of disease. Staging of colon cancer is a careful attempt to find out whether the cancer has spread and, if so, to what parts of the body. More tests may be performed to help determine the stage of colon cancer. Knowing the stage of the disease helps the doctor plan treatment. Colon cancer staging may involve some of the following tests and procedures:

  • Blood tests: The doctor checks for carcinoembryonic antigen (CEA) and other substances in the blood. Some people who have colorectal cancer or other conditions have a high CEA level.

  • Colonoscopy: When a colonoscopy is performed for diagnosis, the doctor examines the entire length of the colon and rectum with a colonoscope to check for other abnormal areas.

  • Endorectal ultrasound: An ultrasound probe is inserted into the rectum. The probe sends out sound waves that people cannot hear. The waves bounce off the rectum and nearby tissues, and a computer uses the echoes to create a picture. The picture shows how deep a rectal tumor has grown or whether the cancer has spread to lymph nodes or other nearby tissues.

  • Chest x-ray: X-rays of the chest can show whether cancer the colon cancer has spread to the lungs.

  • CT scan: An x-ray machine linked to a computer takes a series of detailed pictures of areas inside the body. The patient may receive an injection of dye. Tumors in the liver, lungs, or elsewhere in the body show up on the CT scan.

The doctor also may use other tests (such as MRI) to see whether the colon cancer has spread. Sometimes the staging of colon cancer is not complete until the patient has surgery to remove the tumor.

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