Fine Needle Aspiration of the Thyroid

by Yolanda C. Oertel, M.D. Director, Fine Needle Aspiration Service Cancer Institute, Washington Hospital Center, Washington DC

This material plus many additional questions and answers were published as part of a chapter in the new book The Patient’s Guide to Thyroid Cancer, edited by Douglas Van Nostrand, M.D., Leonard Wartofsky, M.D., and Gary Bloom. This information is provided as an educational service to people being tested for possible thyroid cancer. It is not a substitute for a physician’s care, and you should consult with your physician about any medical condition. Special thanks to the physicians involved in thyroid cancer care at the Washington Hospital Center and the volunteers of ThyCa: Thyroid Cancer Survivors’ Association, Inc., for their assistance in developing this publication.

(c) Copyright 2010 by Yolanda C. Oertel, M.D. All rights reserved. You may print this out for your own use.


Your physician has just told you that you have a “lump” (or nodule) in your thyroid gland. Or you have felt a lump in your neck and have made an appointment to see your primary physician. If you are a woman from about 20 to 50 years old, you should understand that this is a common finding. Nevertheless, you may be concerned about the possibility of cancer. In fact, most nodules or “lumps” in the thyroid are NOT cancerous.

The challenge for the physician is to determine which nodules are benign and which nodules are cancerous. The following qualities may provide useful information, but they will NOT determine whether the nodule is benign or malignant:

  • How long the nodule has been present
  • Whether it is tender or not
  • Whether it feels soft, rubbery, or firm to the touch
  • The blood tests of thyroid function
  • The response to thyroid hormone suppressive therapy
  • Ultrasound findings
  • Thyroid scans and uptake

The only test, prior to surgery, that is proven to differentiate a benign from a malignant nodule is the fine needle aspiration (FNA). Hence, your doctor will tell you that you need a fine needle aspiration of the nodule. What follows is some information about this procedure that will help you understand why and how it will be done.

What is a fine needle aspiration?

It is a simple procedure, similar to drawing blood from your arm. The needle used is thinner than the one for drawing blood and is attached to a syringe in a syringe holder that allows the operator to apply suction easily. Cells from your thyroid lesion will be extracted through this thin needle. If there is fluid in the “lump,” we will drain it. These cells are smeared (spread) on glass slides, stained, and made ready to be examined under the microscope. After examining all the slides, the pathologist will make a cytologic diagnosis and issue a written report.

Do I really need an aspiration?

An FNA is the only non-surgical method of determining whether your thyroid nodule is benign or malignant.

The “tumor is large and has to be removed.” In this instance, do I really need an aspiration (FNA)?

Yes, to avoid surprises for the surgeon. On rare occasions, a patient may have a medullary carcinoma or anaplastic carcinoma of the thyroid. Knowing this in advance will help the surgeon plan accordingly. Additional tests will be needed to exclude the possibility of other tumorssuch as pheochromocytoma.  This is important because pheochromocytomas occur with high frequency in patients with medullary thyroid cancer, and they need to be managed prior to undertaking thyroid surgery. 

Should I have an ultrasound prior to an FNA?

Most of the time it is not necessary. If your physician discovers a nodule and he or she (or the pathologist he or she works with) can perform an aspiration immediately, there is no need to wait for an ultrasound. You may have a diagnosis in 24 hours, and if the nodule is malignant, your appointment with a surgeon can be scheduled within a few days.

What are the possible cytologic results of the FNA?

Usually the results will fall into one of four categories: benign (70-75% of cases), malignant (4-7%), inconclusive (10-15%), and unsatisfactory (1-10%). We will explain the meaning of each of these.

What is a benign diagnosis?

This implies that your nodule or lump is not a malignant tumor. It could be due to inflammation (thyroiditis), accumulated secretion from your gland (colloid nodule), irregular growth of your gland (hyperplastic nodule), or a cyst (fluid-filled nodule).

What is a malignant diagnosis?

This implies that your nodule is cancerous. There are several types of thyroidal cancers. The most common and the easiest to treat successfully is papillary carcinoma.

What is an inconclusive diagnosis?

An inconclusive diagnosis is one for which there is no certainty about the nature of your nodule; it could be either benign or malignant. This means that it is not possible to determine the nature of your lump. Either the FNA has to be repeated or the possibility of surgery should be discussed with your doctor.

What is an unsatisfactory diagnosis?

Whoever performed the FNA was not successful in obtaining enough cells from your thyroid to allow the pathologist to make a diagnosis. Most likely the doctor just obtained blood. It is as if no procedure had been done. The FNA has to be repeated (preferably by a more experienced aspirator). Please make sure that this is not confused with a benign diagnosis.

What are the recommended steps for someone whose results are reported as inconclusive?

The patient should discuss this interpretation with an endocrinologist. If the physician who ordered the FNA is an internist or family practitioner, I suggest that the patient consult an endocrinologist. If the FNA report is inconclusive because the nodule is cellular but not suspicious of malignancy, then the FNA should be repeated. Some endocrinologists believe that a trial of thyroid hormone therapy with subsequent repeat FNA in six to eight months might be appropriate. It might help to have the smears reviewed by another pathologist (second opinion) with a special interest or training in thyroid diseases who might be able to render a more definite diagnosis. If the diagnosis is “follicular neoplasm,” then surgery is indicated.

Could I have cancer that is not detected on FNA?

Yes, because no technique is 100% accurate. If your lump is large and there is a small focus of cancer (next to it or in it), the cancer may not be detected.

What is the accuracy rate of FNA?

The rate of accurate results depends on the skill and experience of the physician obtaining the samples and interpreting the smears under the microscope. The resuts reported in the medical literature vary considerably and may be difficult to interpret accurately.

Who may perform FNAs?

Any physician who is interested in learning how to perform the procedure properly and who has adequate physical facilities (examining table, sink, counter space, slides, slide-holders, etc.). These include endocrinologists and internists, surgeons, pathologists, and radiologists.


Free Booklet Available:

To receive a free copy of the 14-page booklet from which this article was taken, send a request to:

FNA Patient’s Guide
PO Box 571
De Soto, MO 63020

Or e-mail to request a free copy be sent to you.

Last updated:  March 10, 2021