The thyroid biopsy is a procedure in which a sample of thyroid tissue is withdrawn for laboratory examination. The sample can be withdrawn through a needle or a surgical incision may be made to obtain a piece of thyroid tissue.
The test is generally performed when a lump or a nodule is detected in the thyroid. The test may also be ordered if the thyroid gland is enlarged and the cause is not apparent. The biopsy is usually a test for thyroid cancer.
The thyroid is a butterfly-shaped gland located at the base of the neck. It produces thyroxine, a hormone that plays a very crucial role in regulating the metabolism of the body and controlling several vital functions, such as the heart beat, blood pressure, and body temperature. The thyroid also regulates childhood growth and development.
A thyroid biopsy is usually ordered when a painless lump or a nodule is detected, either by the patient or by a doctor during a routine physical examination. A biopsy is the only test that can accurately determine whether the lump is non-cancerous (benign) or cancerous (malignant). The biopsy can be performed in several ways.
The "fine needle aspiration" (FNA) can be done in the doctor's office. An anesthetic is not usually given.
For "large needle biopsy," a mild sedative may be given an hour before the procedure, to relax the patient. The patient will be asked to lie on his or her back, with the head tipped back and the neck extended. The biopsy site will be thoroughly cleansed and the physician will inject a local anesthetic. A small incision (about 1 inch) will be made in the skin. The biopsy needle will be inserted through the incision into the thyroid. A sample of tissue will be removed and the needle withdrawn. Pressure is applied at the biopsy site to stem the bleeding and a bandage applied. This test takes five to ten minutes.
The "open incisional biopsy" is done in an operating room by a surgeon. The patient will be given a general anesthetic. A sedative will be given an hour before the procedure to relax the patient. An intravenous line will be placed in the arm for infusion of fluids or drugs. An endotracheal tube will be inserted through the mouth into the lungs for administering anesthetic gases. After the patient is anesthetized, a small incision is made in the neck. Either the whole thyroid or a part of it is removed. If only a portion is being removed, the surgeon may send a small piece of remaining tissue to the laboratory for immediate testing while the patient is still on the operating table. If the pathologist's report comes back stating that cancer is present in the remaining tissue, the entire thyroid is removed. The incision is closed with stitches. The whole procedure may take about an hour.
The doctor should be informed of any allergies to medications and every medication the patient is taking. If the patient is pregnant, the doctor should be told.
The patient will be asked to sign the necessary consent forms. If a needle biopsy is done, no special preparation is needed. If a large needle biopsy is being done, the doctor may order some tests to determine the clotting ability of the blood. If an open incisional biopsy is being done, a general anesthetic is required and the patient will be asked to refrain from eating or drinking anything 8-12 hours before the test.
The needle used in fine needle aspiration is so thin, the whole procedure feels like a quick injection. There is no pain or tenderness at the site after the test. In large needle biopsy, a stinging needle prick may be felt when the local anesthetic is injected. The site may be sore for a few hours and tender for a day or two after the test.
In the open incisional biopsy, the patient will feel nothing during the procedure, because of the effects of the anesthetic and the sedative. However, the anesthetic may cause the patient to feel drowsy for several hours after the procedure. The anesthetic may also cause the patient to experience some fatigue, and general aches and pains for a day or two after the procedure. The endotracheal tube may make the throat feel mildly sore. If there is swelling at the biopsy site or if the patient develops a fever, the doctor should be notified immediately.
No risks are associated with fine needle aspiration. Large needle biopsy may cause bleeding into the thyroid gland. There is a small risk that the anesthetic used in open surgical biopsy may cause a life-threatening reaction.
The normal appearance and architecture of the thyroid cells indicate that no cancer cells are present in the thyroid tissue.
Any abnormalities of the thyroid tissue cells may indicate cancer, benign tumors, or some other thyroid disease. If cancer is suspected, the pathologist may do some more testing to identify the extent of the cancer so that it can be treated appropriately.
The Patient's Guide to Medical Tests. Ed. Barry L. Zaret, et al. Boston: Houghton Mifflin, 1997.
Sobel, David S., and Tom Ferguson. The People's Book of Medical Tests. New York: Summit Books, 1985.
American Thyroid Association, Inc. Montefiore Medical Center, 111 East 210th St., Bronx, NY 10467. <http://thyroid.org>.
Thyroid Foundation of America, Inc. Ruth Sleeper Hall, RSL 350, 40 Parkman St., Boston, MA 02114-2698. (800) 832-8321.
Lata Cherath, PhD
Biopsy—The surgical removal and microscopic examination of living tissue for diagnostic purposes.
Endotracheal tube—A hollow tube that is inserted into the windpipe (trachea), leading to the lungs.
Pathologist—A doctor who specializes in the diagnosis of disease by studying cells and tissues under a microscope.