What is Ultrasound-Guided Thyroid Fine Needle Aspiration (FNA) Biopsy?
Thyroid fine needle aspiration (FNA) biopsy is the only non-surgical method that can differentiate malignant and benign thyroid nodules.
Your doctor slides the ultrasound probe back and forth over your thyroid gland to determine precisely which area to biopsy. An injection of an anesthetic solution (lidocaine) is usually used to numb the skin first. You will feel a pinch and burn while the anesthetic begins to work.
Using ultrasound to guide the needle tip, your doctor then inserts a thin needle into your thyroid gland and removes a small amount of soft tissue, thyroid cells, and fluid through the needle. The ultrasound increases the quality of the biopsy specimens and allows the doctor to know where the needle tip is at all times.
After each pass with the needle, the material from your thyroid gland is placed on a glass microscope slide and sent to the cytology laboratory for examination. Your doctor may perform 4-6 passes of the thyroid nodule to get an adequate specimen.
During a needle biopsy, you may feel pressure or a brief, sharp pain in your neck as the needle enters your thyroid gland. Try not to swallow, cough, or make sudden movements when the needle is in your neck to prevent injury. You do not need to hold your breath during the biopsy, but stay calm and still.
There is usually no bleeding after the procedure. A small bandage is applied where the needle was inserted. The area may remain sore for up to 24 hours after the biopsy. Ice packs relieve pain in most cases, but Tylenol can also be used. Ibuprofen should be avoided as it could increase the risk of bleeding.
Do I Need an Ultrasound-Guided Fine Needle Aspiration Biopsy?
Patients with thyroid nodules may need to undergo an ultrasound-guided FNA biopsy if the thyroid nodule is larger than 1-1.5 cm (⅜-⅝ inch) and/or has any worrisome characteristics.
For high-risk patients (those who have had radiation exposure in the past or have a family member with thyroid cancer), nodules under 1 cm may need a biopsy.
How to Prepare for an Ultrasound-Guided FNA Biopsy
Your doctor will ask you to stop taking anticoagulants (or blood-thinners) like warfarin or heparin for several days before the biopsy to prepare for thyroid FNA. This reduces the risk of bleeding during and after treatment. You can continue to take any other essential medications. In most cases, you do not need to fast on the day of your treatment.
The ultrasound gel is water-based and non-toxic. However, you should avoid wearing jewelry around your neck and wear comfortable clothes on the day of your appointment to prevent accidental damage.
What are the Possible Results of an Ultrasound-Guided FNA Biopsy?
The specimens collected during a biopsy are analyzed by a cytopathologist and evaluated by your endocrinologist. The Bethesda System for Reporting Thyroid Cytopathology classifies your results into one of six categories.
Benign thyroid nodules are the most common type of abnormal growth detected using a biopsy. If you have benign nodules, your doctor may continue to monitor them for several months.
If the nodules are large or causing you to experience difficulties breathing, speaking, or swallowing, your doctor may recommend a thyroid radiofrequency ablation (RFA) treatment to encourage cystic degeneration.
In up to 7% of cases, the biopsy will show cancerous or malignant thyroid nodules. Most malignant thyroid nodules turn out to be papillary thyroid cancer and require a full or partial thyroidectomy or radioactive iodine treatment to eliminate the cancerous cells.
Suspicious for malignancy
If a biopsy shows that the tissue is suspicious for malignancy, there is a 65-70% chance that the malignant thyroid nodules are cancerous. The tissue specimen may display malignant characteristics like microcalcifications or irregular margins and benign features such as a uniform halo and no vascular structures.
A non-diagnostic result means that there were insufficient cells available for diagnosis. This can occur when there is too much blood or cystic fluid in the sample and not enough thyroid follicular cells. If your results are non-diagnostic, your doctor may recommend a repeat biopsy.
Follicular neoplasm or Suspicious for follicular neoplasm
The follicular neoplasm is indicative of both cancerous and non-cancerous growth and is often referred to as indeterminate. This could suggest that the patient has a benign adenomatoid nodule, a follicular adenoma, or a non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).
It could also indicate that the patient has a growth with a high risk for malignancy, such as follicular carcinoma or a follicular variant of papillary thyroid carcinoma.
Your doctor may recommend repeat biopsies or genetic testing to confirm the diagnosis.
Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS)
These results are also referred to as indeterminants. Indeterminate specimens show characteristics of benign thyroid nodules and malignant thyroid nodules and require further testing.
Genetic Markers for Indeterminate Thyroid Nodules
An ultrasound-guided FNA biopsy has more than 95% diagnostic accuracy. However, the diagnosis is still unclear when a patient has a thyroid FNA biopsy with an indeterminate result.
Indeterminate results on thyroid FNA samples are common (5-15% of biopsies). The American Thyroid Association recommends that most nodules require surgical removal if repeated biopsies also prove indeterminate.
Are There Any Risks of a Thyroid FNA Biopsy?
A thyroid FNA biopsy is a very safe procedure and is recommended by the American Thyroid Association as the standard non-surgical diagnostic tool for confirming malignant growths.
However, there are some minor risks associated with the procedure, including:
- Bleeding at the needle insertion site
- Mild infection
- Damage to structures close to the thyroid
Thyroid Cancer Diagnosis and Treatment Options
If your endocrinologist has confirmed a thyroid cancer diagnosis with an ultrasound and FNA biopsy, they’ll proceed to stage the cancer’s development so that your medical care team can create an optimal treatment plan which may include surgical removal, radioactive iodine ablation, and radiotherapy or chemotherapy.
There are two common types of thyroid cancers, papillary and follicular thyroid cancer, making up approximately 95% of all thyroid cancers. These cancers are staged into two categories if you are under 55.
- Stage I: Cancer is contained within the neck
- Stage II: Cancer has spread outside the neck to other organs
If you are over 55, thyroid cancer is categorized into several stages:
- Stage I: Any thyroid cancer less than 2 cm that is not growing outside the thyroid and has not spread to the body’s cervical lymph nodes or other areas.
- Stage II: The thyroid cancer is between 2 and 4 cm but is not growing outside the thyroid or spreading to nearby lymph nodes or other areas of the body.
- Stage III: thyroid cancer is larger than 4 cm or has grown slightly outside the thyroid (T3). The It may or may not have spread to nearby lymph nodes or other areas of the body.
- Stage IV: The cancer has grown beyond the thyroid gland and into nearby neck tissues. It might or might not have spread to nearby lymph nodes, including the upper chest (superior mediastinal nodes) and throat (retropharyngeal nodes).
It also may or may not have spread to other areas of the body. The cancer may have also grown either back toward the spine or nearby large blood vessels. Stage IV thyroid cancer has the highest mortality rate and requires extensive surgical and non-surgical treatment.
Contact Associated Endocrinologists
If you experience thyroid nodule symptoms, contact Associated Endocrinologists for an appointment. Our experienced healthcare professionals can perform a thyroid scan, thyroid ultrasound, or guided FNA biopsy to help with the evaluation of thyroid nodules. We can also discuss treatment options such as radioactive iodine or thyroid RFA to eliminate malignant lesions and noncancerous nodules.