Diagnosis and staging includes tests to find out if you have colon or rectal cancer, where it is, and how far it has spread in your colon and beyond it. Here are some of the common tests.
- Colonoscopy to visualize the entire colon. A complete colonoscopy is necessary even if the original cancer was diagnosed by sigmoidoscopy or some other method. It is not uncommon for more than one cancer to be present in the colon. During colonoscopy, biopsies of the tumor and any other suspicious tissue may be obtained for evaluation.
- Physical examination and medical history. Doctors look for tenderness, swelling, or unusual growths, but they also are evaluating your overall health.
- Family medical history. Some colorectal cancers are inherited and a good family history, spanning three generations, is important.
- Imaging studies to find potential spread to other organs:
- CT-scans of abdomen and pelvis.
- Chest x-ray or CT scan
- Ultrasound examination of the rectum to evaluate the extent of rectal tumors.
- MRI (magnetic resonance imaging) may be a more sensitive scan of some tissues. This may not be required.
- PET scans (positron emission tomography) may help locate areas of cancer activity that cannot be seen on CT or MRI. This may not be required.
- Blood tests, including a complete blood count (CBC) to evaluate possible anemia caused by a bleeding tumor and tests to find out how well your liver is functioning.
- CEA (carcinoembryonic antigen) levels in the blood. CEA, a tumor marker, is not always high in patients with colorectal cancer and it can be elevated for other reasons. However, baseline CEA information can help to monitor changes during treatment and an increased level may be the first signal of a later recurrence.
- The surgeon will look and feel for other tumors in the abdomen and remove suspicious tissue for biopsy.
- The tumor, tissue on either side of it (the margins), and fat and lymph nodes attached to the colon or rectum are removed for further study by a pathologist. If possible, your surgeon should remove at least 12 nodes for examination by the pathologist. This may not be possible for patients who have received treatment (for example, with radiation and chemotherapy) prior to surgery.
- The pathologist evaluates the type of cancer cells in the tumor itself, looks for cancer in the margins and other nearby tissues, and studies as many lymph nodes as possible for the presence of cancer. Again, at least 12 nodes be resected and examined.
The results of the pathologist’s examination of lymph nodes and other tissue will help to determine the stage of disease.