The only sure way to determine whether a tumor is malignant is to take a sample of the tumor and examine it under the microscope. This procedure is called a biopsy. When an abnormal growth is found during a colonoscopy, it can usually be biopsied immediately, through the same instrument that is being used for the examination. The tissue samples obtained during the biopsy are sent to be examined under a microscope by a specialist in tumor identification: the pathologist.
A pathologist’s report will usually include the following information:
Polyp site—where in the bowel it was found.
Polyp size—the larger the polyp, the greater the possibility that it contains cancer.
Polyp configuration—the general shape of the poly. Polyps with a stalk (polypoid) are less suspicious than those without (sessile).
Histologic type—the type of cells in the tumor. Tumors made up of glandular cells–adenocarcinomas–are the most common type of colon cancer.
Histologic grade—how different the cancer cells look from normal cells is a good indication of how aggressive (“bad”) they are.
Invasion—how deeply the cancer penetrates healthy tissue.
If you go on to have surgery to remove the cancer, the surgeon will send whatever portion of colon or rectum she removes to the pathologist. With this additional information the pathologist will then create a final report. This report will specify the actual size of the tumor, the exact type of cells, and the status of the tumor edges, or margins. Presence of cancerous cells at the edges is an indication that some cancer might have been left behind. If your surgeon removed lymph nodes for examination, the report will also specify whether cancer cells have reached them.
At some point before or after surgery, you will probably have additional tests.
Why more tests? A biopsy can confirm that the diagnosis is cancer, but it will not show whether the cancer has spread to other parts of the body. This information is vital, because it will help your medical team determine what kind of treatment is called for to achieve the best results possible in your particular case.
The tests may include:
Chest x-rays Tumors that have spread to the lungs can often be seen on chest x-rays.
Blood tests Carcinoembryonic antigen (CEA) is a protein that is produced by colon cancer cells. Currently, doctors measure a person’s CEA level before and after surgery to help determine whether the procedure has completely removed the cancer. After surgery, your CEA level should be normal. If your CEA level increases steadily after surgery, it may be an indication that the cancer has returned.
Liver function tests will indicate whether the cancer has damaged the liver—a common site for colon cancer spread.
PET Scan PET scans use small amounts of radioactive tracer and a special camera to obtain information about tissue function. The resulting images help physicians distinguish metastases from normal tissue, and play a very important part in tumor staging.
CT Scan CAT scan, CT scan, or Computerized Axial Tomography all mean the same thing. This test uses ordinary xrays, and a rotating film/source system to obtain detailed, three dimensional images of your body. The test is painless and takes less than an hour.
MRI Scan MRI or Magnetic Resonance Imaging uses a combination of magnetic energy and ordinary radio waves to create images of the inside of your body. It is generally not done unless the CT scan was indefinite, or there is a need to see the liver better.
Because the MRI unit can feel cramped, notify the technologist or your physician if you feel uncomfortable in confined spaces. MRI is painless, and does not expose you to x-ray radiation. The test takes about an hour.