What is a fine needle aspiration biopsy?

A fine needle aspiration biopsy samples a thyroid nodule to help determine if it is cancer or not. In the procedure, a small needle is passed through the skin into the thyroid nodule, and suction is applied to the syringe as the needle is moved up and down within the nodule. This aspiration process draws a sample of cells and other material up through the needle into the syringe. The needle is then removed and the sample is placed on a glass slide where it can be stained and examined under a microscope

What information can it provide?

In many instances, a fine needle aspiration biopsy can indicate whether or not a thyroid nodule is likely to be thyroid cancer. Most samples are made up of two distinct components, epithelial cells and colloid. Epithelial cells are the predominant cells present in the tissue of the thyroid gland. In normal tissue, they are arranged in spherical formations called follicles. These follicles are filled with colloid, a viscous substance containing the hormones produced by the thyroid gland. When a sample from an aspiration is examined under a microscope, a pathologist is able to evaluate the features of individual epithelial cells, the patterns formed by groups of epithelial cells, and the amount of colloid present to determine whether a sample represents normal or abnormal tissue. Abnormal tissue patterns can be further evaluated to determine whether they are suspicious for thyroid cancer.

In general, there are four diagnostic categories for samples from fine needle aspiration biopsies.

Benign- indicating that a sample is consistent with a benign thyroid nodule that is not cancer

Malignant- indicating that a sample is almost certainly thyroid cancer

Suspicious or Indeterminate- indicating that a sample may either be benign or thyroid cancer. Nodules with such findings cannot be reliably diagnosed by fine needle aspiration biopsy findings alone. Most (~ 80%) are benign, but a minority (~ 20%) are cancer. Further steps are usually required for these patients.

Inadequate- indicating that there is not enough material in a sample to draw accurate conclusions

How is it done?

A fine needle aspiration biopsy is an outpatient procedure performed while the patient is awake. The patient usually lies back on a stretcher or table with a pillow placed under the neck or between the shoulder blades to arch the neck upwards. A gown or towel may be placed over the chest. The area of the neck where the thyroid nodule is located is carefully palpated, and then cleaned with antiseptic. Local anesthetic may be injected into the skin over the thyroid nodule, although many practitioners prefer to perform aspirations without any anesthetic. The patient is then asked to hold still and to refrain from swallowing as the needle is inserted through the skin and into the thyroid nodule. Suction is applied with the syringe, and the needle is moved up and down inside the thyroid nodule until enough material has been drawn up into the tip of the syringe. The needle is then removed, pressure is applied to the biopsy site. The biopsy material in the syringe is sprayed onto a glass slide. In practice, a number of samples are usually taken in separate aspirations to improve the chances that an adequate sample will be obtained. In some facilities, a pathologist may be on hand to immediately stain and examine each sample to see if it contains enough cells and colloid to make a diagnosis. After a fine needle aspiration biopsy is completed, the site is cleaned off and a band-aid is applied.

Are there any possible complications?

In experienced hands, complications of a fine needle aspiration biopsy are rare. There is no need to skip meals before or after a fine needle aspiration biopsy. Most patients carry on with usual daily activities after the procedure. There may be some bruising at the site following the procedure. Sometimes there is aching in the neck after the procedure. This can be relieved with a medication like acetaminophen (Tylenol).

In some situations, a thyroid nodule may be difficult to palpate, or may lie very close to important structures in the neck. In these situations, ultrasound may be used to guide the tip of the needle to allow for precise sampling of thyroid nodules and to minimize the risk of damaging nearby structures.

Who should perform a fine needle aspiration biopsy?

Fine needle aspiration biopsies may be performed by a number of different practitioners. Most endocrinologists who treat patients with thyroid conditions are experienced at performing aspirations. Some surgeons, otorhinolaryngologists (also referred to as ear, nose and throat surgeons, or head and neck surgeons), and pathologists are also skilled at performing the procedure. Aspirations that require ultrasound guidance may be performed by radiologists who specialize in this area.

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