Fine-Needle Aspiration Biopsy of the Thyroid (cont.)
Ruchi Mathur, MD, FRCP(C)
Ruchi Mathur, MD, FRCP(C) is an Attending Physician with the Division of Endocrinology, Diabetes and Metabolism and Associate Director of Clinical Research, Recruitment and Phenotyping with the Center for Androgen Related Disorders, Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What are thyroid nodules?
- What is the initial assessment of a thyroid nodule?
- Fine needle aspiration biopsy (FNAB) of the thyroid gland - why is it done?
- Should fine needle aspiration biopsy be done on all thyroid nodules?
- How is fine needle aspiration biopsy performed?
- What are the complications of fine needle aspiration biopsy of the thyroid?
- What happens to the thyroid tissue obtained at the fine needle aspiration biopsy?
- Fine Needle Aspiration Biopsy At A Glance
Fine needle aspiration biopsy (FNAB) of the thyroid gland why is it done?
A biopsy to obtain tissue for analysis is the best technique for detecting or ruling out the presence of cancer. For many years, a core biopsy of the thyroid was the procedure of choice. This method involved a large biopsy, which was often more difficult for patients. fine needle aspiration biopsy has now become the method of choice for obtaining samples of thyroid tissue. The procedure is technically quite simple. When performed properly, the testing has a false negative rate of less than 5%. This means that a positive finding, such as cancer, will be missed fewer than five times out of 100.
The fine needle aspiration is also performed to treat thyroid cysts. A thyroid cyst is a fluid-filled sac within the thyroid gland. Aspiration of the cyst with a needle and syringe can shrink the swelling from the cyst and the fluid removed can be analyzed for cancer.
Should fine needle aspiration biopsy be done on all thyroid nodules?
There are certain situations in which your physician may elect not to perform a biopsy of a nodule. For example, in a patient with an over- active thyroid (hyperthyroidism), the chance for a nodule to be cancerous is significantly less, particularly if other studies (such as nuclear thyroid imaging) show that the nodule is producing thyroid hormone (a "hot" nodule).
A doctor may recommend fine needle aspiration biopsy of the thyroid in the following situations:
- To make a diagnosis of a thyroid nodule;
- To help select therapy for a thyroid nodule;
- To drain a cyst that may be causing pain; or
- To inject a medication to shrink a recurrent cyst.
How is fine needle aspiration biopsy performed?
In most cases, if the nodule can be felt, a biopsy can be performed in the doctors office. In some cases an ultrasound may be needed to help guide the biopsy. For example, if the nodule cannot be felt without difficulty or if the nodule has areas within it that specifically should be biopsied.
Little preparation by the patient is required. There is no need to fast or to withhold medications on the day of the biopsy. Occasionally, though, a patient may be asked not to take blood thinning medication on the day of the biopsy. After an examination to pinpoint the nodule, the patient is asked to lie down and the neck is exposed. Depending on the location of the nodule and the type of clothes the patient is wearing, he or she may be asked to change into a gown. The doctor drapes the area around the neck and cleans the neck off. This is usually done with iodine, which is a brown liquid that sterilizes the skin. Some doctors may choose to inject a local anesthetic. Often, the injection of the anesthetic results in an initial discomfort, like a bee sting. The majority of doctors who regularly perform fine needle aspiration biopsies of the thyroid do not use a local anesthetic for this reason. Since the needle used for fine needle aspiration biopsy is so fine, anesthesia often results in simply another uncomfortable poke for the patient. If a patient is particularly concerned and nervous, a topical anesthetic preparation may be applied, which takes 10 to 20 minutes to work, thus prolonging the procedure. A patient undergoing fine needle aspiration biopsy should discuss any preferences for local anesthetic before the procedure begins. Most patients undergoing fine needle aspiration biopsy forego the use of any anesthetic and do very well.
Once the patient is ready, a small, fine-gauge needle is inserted into the nodule. The needle is smaller in diameter than the needle used in most blood draws (usually a 25 gauge 1.5 inch needle). The patient holds his breath while the needle is rocked gently to obtain as much tissue as possible. (The reason for holding the breath is to minimize movement of the structures in the neck.) The needle is then withdrawn and pressure is applied over the thyroid area to minimize bleeding. This procedure is usually repeated four to six times to ensure that an adequate amount of tissue has been collected. After the procedure, pressure is applied over the neck area for 5 to 10 minutes to assure that the bleeding has stopped. The pressure also helps to reduce any swelling that may occur. The entire procedure usually takes less than 20 minutes.
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