A biopsy is the removal of cells or tissue to be examined under a microscope. This exam can show whether the tissue is cancerous. For colorectal cancer, the most common type of biopsy is an endoscopic biopsy. Other types of biopsies that your doctor may use include a needle biopsy and a surgical biopsy. Needle biopsies are sometimes used to see if the cancer has spread. Surgical biopsies are used to take samples of large tumors. They are also used for tumors in a hard-to-reach place.
Once your doctor removes the tissue, he or she sends it to a lab. There, a doctor called a pathologist looks at the tissue under a microscope to check for cancer cells. It usually takes several days for the results of your biopsy to come back. A biopsy is the only sure way to tell if you have cancer and the only way to tell what kind of cancer it is.
Here are descriptions of the 3 types of biopsies your doctor may do.
Endoscopic biopsy. The most common biopsy done to diagnose colorectal cancer is one performed during a colonoscopy or a sigmoidoscopy. These are screening and diagnostic tests that use an endoscope. An endoscope is a tube with a video camera used to look inside your rectum and colon. There are specific types of endoscopes used depending on what part of your body the doctor is looking at. For a colonoscopy, the doctor uses a colonoscope. For a sigmoidoscopy, the doctor uses a sigmoidoscope. If the doctor finds a polyp during one of these tests, he or she most likely will remove it. After cutting it from your colon wall, the doctor will take it out through the tube being used to see inside you. The removal is called a polypectomy. Your doctor then sends the polyp to the lab to be checked for cancer. If the doctor sees a mass or some other type of unusual tissue, he or she will remove a portion of it through the tube and send it to the lab. The lab will then be able to determine whether it is cancer.
Needle biopsy. There are 2 types of needle biopsies. One is a fine needle biopsy. For it, the doctor uses a fine needle and syringe to remove liquid and a very small sample of tissue. The other is a core needle biopsy. The needle for this procedure is slightly larger. The doctor takes out a small sample of tissue about 1/16 of an inch in diameter. These biopsies are sometimes done to examine tissue from a tumor or a mass the doctor has found in some other part of your body. They can help the doctor know whether the cancer has spread. To perform a needle biopsy, the doctor inserts a needle into the tumor and withdraws a sample of tissue. The biopsy can be done in the doctor's office using a local anesthetic for tumors the doctor can feel. For tumors that can't be felt, the doctor may use a CT scan to help guide the placing of the needle. CT scans are very accurate X-rays that take three-dimensional pictures of the inside of your body. Sometimes doctors use an ultrasound image to help guide the insertion of the needle. A needle biopsy takes only a few moments. It doesn't require you to stay in the hospital overnight.
Surgical biopsy. Most biopsies can be performed with one of the above techniques. However, if the polyp or the mass the doctor wants to examine is large or in a hard-to-reach spot, you may need to have surgery. You'll be given a general anesthesia so that you fall asleep and don't feel anything. You will also probably have to stay overnight in the hospital. It may take several days before you can go back to your normal routine. Sometimes you need a formal surgical procedure even for a biopsy.
Most polyps are benign. That means they are not cancerous. Microscopic examination will reveal the nature of the polyps and whether dysplasia, which is abnormal cell growth, or carcinoma, which is cancer, is present. If you do not have cancer but do have a dysplastic polyp, you are at higher risk for developing more polyps or even cancer. Doctors, like all people, have their own ways to communicate. Your doctor may have to tell you the results of your biopsy over the phone. Or your doctor may wait to tell you at your next appointment. If there is a way you would like to be told about the results of your tests in the future, let your doctor know.
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