What Is a Thyroid Biopsy?
A thyroid biopsy is a procedure where a small sample of fluid and cells is taken from a nodule in the thyroid gland using a fine needle. The thyroid gland is located in the front middle section of the neck and is a butterfly-shaped organ with two lobes connected by a central portion.
Nodules or other abnormalities in the thyroid are typically detected using imaging methods such as ultrasound and Doppler. However, it is not always possible to determine whether a nodule is benign (non-cancerous) or malignant (cancerous) using only imaging methods.
Thyroid biopsy is also known as needle biopsy, needle aspiration, fine needle biopsy, or fine needle aspiration. A thyroid biopsy is a minimally invasive method used to collect a sample of cells from a suspicious nodule, which is then examined under a microscope to determine if it is benign or malignant.
What Is the Thyroid Gland?
The thyroid gland is a butterfly-shaped endocrine gland located in the lower front part of the neck. The thyroid’s role is to produce thyroid hormones that are secreted into the bloodstream and carried to every tissue in the body. These hormones help regulate the body’s energy use, maintain warmth, and ensure that the brain, heart, muscles, and other organs function properly.
Which Thyroid Nodules Need a Biopsy?
A thyroid biopsy is performed to understand the nature of a nodule in the thyroid gland. Not every thyroid nodule requires a biopsy. When a nodule is detected in the thyroid, and imaging methods suggest a suspicious condition, a biopsy is performed to clarify the situation and guide treatment accordingly.
Thyroid nodules are common, and by the age of 50, most people will have at least one thyroid nodule. The prevalence of thyroid nodules increases with age. For instance, approximately 60% of individuals aged 50 and 80% of those aged 70 will have a thyroid nodule. But who should undergo a thyroid nodule biopsy? The answer is that any nodule that a doctor suspects may be cancerous should undergo a fine-needle aspiration biopsy. Doctors look for certain characteristics of thyroid nodules that may indicate concern;
A fine-needle aspiration biopsy is typically performed on any thyroid nodule large enough to feel, which is usually more than 1 centimeter in size.
A biopsy is also indicated for any thyroid nodule that causes symptoms.
These symptoms may include: a swelling you can feel or see in the neck area; difficulty swallowing or a sensation of something stuck in your throat; a persistent cough; frequent coughing and clearing your throat throughout the day; pressure in the airway (trachea); or hyperthyroidism symptoms (indicating elevated thyroid hormone levels).
A fine-needle aspiration biopsy should be performed on any swollen or abnormal lymph nodes in the neck. This might be more accurate than a biopsy of the thyroid nodule itself for diagnosing thyroid cancer.
A biopsy should be performed on nodules with specific characteristics, as seen on ultrasound.
Is Preparation Needed for a Thyroid Biopsy?
Usually, no special preparation is required, and it can be performed at any time. For children, sedation may be used during the biopsy.
Most medications can be continued. However, anticoagulants, also known as “blood thinners,” may need to be temporarily stopped before the biopsy to reduce the risk of bleeding. Consult your doctor for guidance on when to stop these medications. If you have any questions about taking your medications before the thyroid biopsy, be sure to talk to your doctor.
In general, you will not need to fast on the day of your appointment. During the thyroid biopsy, ultrasound gel will be applied to the neck to obtain ultrasound images. This gel is water-soluble and non-toxic but may stain clothes or jewelry. Therefore, it may be necessary to wear comfortable clothing and remove jewelry from around your neck for the procedure.
The needle used during a thyroid biopsy is smaller and finer than the one typically used to draw blood from your arm for lab tests. An ultrasound device is used to guide the needle into the nodule within the thyroid.
The Thyroid Biopsy Procedure
First, the thyroid gland and nodule are examined again using ultrasound. The entry point for the needle is determined. The skin over the neck is cleaned with an antiseptic. Local anesthesia is administered to numb the area.
An experienced radiologist who has performed thousands of these procedures will use ultrasound guidance to insert a needle through the skin and into the nodule. A small amount of fluid and cells is collected from the nodule, completing the procedure. If there are multiple nodules in the thyroid, this procedure may need to be repeated for each one. The entire process is usually completed in less than 30 minutes.
A fine-needle aspiration biopsy of a thyroid nodule is a simple and safe procedure performed in the doctor’s office. Typically, the biopsy is performed with ultrasound guidance to ensure the needle is placed accurately into the thyroid nodule. You will be asked to lie on your back with your head tilted backward to extend your neck. Sometimes, a pillow is placed under your shoulders to help you achieve the best position for the biopsy.
You may feel some pressure on your neck from the ultrasound probe and needle during the procedure. You will be asked to remain as still as possible and avoid coughing, talking, and swallowing during the biopsy.
How Is a Thyroid Biopsy Performed?
The neck will first be cleaned with an antiseptic. Local or topical anesthesia may be applied. For the biopsy, your doctor will use a very fine needle to take cells from the thyroid nodule. The needle used is smaller than those typically used for blood draws. Your doctor will insert the needle through the skin into the thyroid nodule. After sampling, which takes only a few seconds, the needle will be removed. New needles will be used for additional samples. Typically, two to six passes with the fine needle are made in different parts of the nodule to obtain several cell samples. This increases the chances of finding cancerous cells if they are present. If there is fluid in the nodule, a syringe may be used to drain it.
After the biopsy, pressure will be applied to the neck. The procedure generally takes less than 30 minutes.
What Happens After a Thyroid Biopsy?
The procedure is typically done with local anesthesia, and the patient remains conscious. After the procedure, you will be asked to sit up slowly to prevent dizziness. Most patients leave feeling fine. There are usually very few restrictions on what you can do after a thyroid biopsy, so it is generally not necessary to bring someone to assist you or drive you home.
A little neck discomfort at the biopsy site is expected after the procedure.
Possible Results of a Thyroid Biopsy
The results of a thyroid biopsy are reported based on the Bethesda System for Reporting Thyroid Cytopathology, with six possible diagnoses. Please note that percentages may vary slightly between institutions and centers.
Benign
This category accounts for up to 70% of biopsies when using the Bethesda System (one of the most common ways cytopathologists classify nodule biopsy samples). The risk of malignancy in this group is typically less than 3%. These nodules are generally monitored with a follow-up ultrasound within 18 months and periodically afterward if necessary.
Malignant (Cancerous)
This category accounts for 3-7% of all biopsy samples. The most common type of thyroid cancer found in these biopsies is papillary thyroid cancer. When a biopsy result is malignant, there is a 97-99% chance that the lesion is truly cancerous. Almost all of these nodules will require surgery (thyroidectomy).
Suspicious for Malignancy
When a biopsy result is suspicious for malignancy, there is a 60-75% chance of cancer. The cytopathologist will see features of concern but not enough for a cancer diagnosis. Treatment typically involves surgery.
Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS)
This category is alternatively referred to as “indeterminate.” These samples have some concerning features and some that appear more benign. Although there are some differences between institutions, this diagnosis carries a 5-15% risk of malignancy. In these cases, repeat biopsies and/or genetic testing may be helpful.
Follicular Neoplasm or ‘Suspicious for Follicular Neoplasm’
This category is alternatively referred to as “indeterminate.” It carries a 15-30% risk of malignancy. It is challenging to determine whether these nodules are benign or malignant without removal. In such cases, genetic testing may be helpful. If necessary, surgery may involve removing half of the thyroid (the side with the nodule) for diagnosis and treatment.
Nondiagnostic
This means that there were not enough cells in the sample to make a diagnosis. Despite all efforts and even if the needle is in the nodule during the biopsy, there are times when the sample does not contain enough thyroid follicular cells to make a correct diagnosis. Nondiagnostic samples can also occur for other reasons, such as obtaining only cyst fluid or when there is a lot of blood present. In these cases