Fine-Needle Aspiration Biopsy of the Thyroid (cont.)
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.
Next: What are the complications of fine needle aspiration biopsy of the thyroid? »
- Thyroid Blood Tests - Read about thyroid blood tests, which are used to diagnose disease of the thyroid such as hyperthyroidism and hyperthyroidism, as well as point to other diseases of the thyroid gland.
- Hypothyroidism - Learn about Hypothyroidism (underactive thyroid) including causes, symptoms (such as weight gain, fatigue, and depression), diagnosis, and treatment.
- Thyroid Scan - Learn about a thyroid scan, a procedure to assist in diagnosing, hypothyroidism, thyroiditis, hyperthyroidism, thyroid nodules, and thyroid cancer.
Latest Medical News
Thyroid RSS