Thyroid nodules are common
A thyroid nodule is a lump or growth in the thyroid, the butterfly-shaped gland at the front of your neck. Nodules are very common. Some are felt during an exam, but many are found by chance on an ultrasound, CT or MRI done for another reason. When high-resolution ultrasound is used, nodules are found in a large share of adults, and they become more common with age.1
Most nodules are benign (not cancer). In the American Thyroid Association (ATA) guidelines, thyroid cancer is found in roughly 7% to 15% of nodules that are evaluated, depending on factors such as age, sex, radiation exposure and family history.1
Step 1: A blood test for thyroid function
The first test is usually a TSH (thyroid-stimulating hormone) blood test. It shows whether the thyroid is making too much, too little or the right amount of hormone.1
- If TSH is low, the nodule may be making extra thyroid hormone on its own (a "hot" or hyperfunctioning nodule). A thyroid scan is often the next step. Hot nodules are rarely cancer and usually don't need a biopsy.
- If TSH is normal or high, the next step is usually a dedicated thyroid ultrasound.
Step 2: Thyroid ultrasound
Ultrasound is the key test for nodules. It's painless, uses sound waves (no radiation), and shows the size and appearance of each nodule and the nearby lymph nodes.1
The radiologist looks at features such as whether the nodule is solid or fluid-filled, how bright or dark it looks, the shape and edges, and whether it has tiny bright spots. Many reports use a scoring system called ACR TI-RADS, which groups nodules from TR1 (benign) to TR5 (highly suspicious).2 The ATA uses a similar set of "patterns," from benign to high suspicion.1
Step 3: Deciding whether to biopsy
Not every nodule needs a needle biopsy. The decision depends on both the pattern on ultrasound and the size. As a general guide from the ATA:1
| Ultrasound pattern | Biopsy usually considered at |
|---|---|
| High or intermediate suspicion | 1 cm or larger |
| Low suspicion | 1.5 cm or larger |
| Very low suspicion (for example, spongiform) | 2 cm or larger, or watch with ultrasound instead |
| Purely cystic (fluid only) | Not needed for diagnosis |
Nodules smaller than 1 cm are usually watched rather than biopsied, unless there are other concerns such as suspicious lymph nodes. TI-RADS uses slightly different size cutoffs, so your plan may be based on either system.2
What a fine-needle aspiration (FNA) is like
A fine-needle aspiration uses a very thin needle, guided by ultrasound, to collect a small sample of cells. It's done in an outpatient setting, usually takes a few minutes per nodule, and most people go back to normal activities the same day. Some soreness or a small bruise is common. At Capital Diabetes & Endocrine Associates, the practice lists thyroid nodule FNAs performed by pathologists at its Silver Spring and Camp Springs offices.
Before the procedure, tell the team if you take blood thinners, and follow any instructions you're given about them. Don't stop a blood thinner on your own.
Understanding Bethesda results
Thyroid FNA results are reported using the Bethesda System, updated in 2023. It has six categories:3
- Nondiagnostic: not enough cells. The biopsy is often repeated.
- Benign: the most common result. Usually followed with periodic ultrasound.
- Atypia of undetermined significance (AUS): some cells look unusual, but it's not clear why.
- Follicular neoplasm: a pattern that can be benign or cancer and can't be sorted out by cells alone.
- Suspicious for malignancy: features suggest cancer, but not for certain.
- Malignant: cancer cells are seen, most often papillary thyroid cancer.
For the "in-between" results (categories 3 and 4), options may include repeating the FNA, molecular testing of the sample, or surgery to remove part of the thyroid. Your clinician will talk through the pros and cons with you.1
Follow-up and outlook
Benign nodules are usually followed with repeat ultrasound. How often depends on the ultrasound pattern; for very low-risk nodules, follow-up may be spaced years apart.1 If a nodule grows a lot or changes appearance, a repeat biopsy may be suggested.
If cancer is found, most differentiated thyroid cancers have an excellent outlook. Treatment is guided by updated 2025 ATA guidelines, which focus on matching the extent of treatment to each person's risk.4
When to call sooner
Let your clinician know promptly if you notice a nodule growing quickly, new hoarseness that doesn't go away, trouble swallowing, or new lumps in the neck. Trouble breathing is an emergency: call 911.
This article is general education. Your plan depends on your own ultrasound, lab results and history.
Sources & references
- Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016;26(1):1–133. doi:10.1089/thy.2015.0020. View source
- Tessler FN, Middleton WD, Grant EG, et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): white paper of the ACR TI-RADS Committee. J Am Coll Radiol. 2017;14(5):587–595. doi:10.1016/j.jacr.2017.01.046. View source
- Ali SZ, Baloch ZW, Cochand-Priollet B, Schmitt FC, Vielh P, VanderLaan PA. The 2023 Bethesda System for Reporting Thyroid Cytopathology. Thyroid. 2023;33(9):1039–1044. doi:10.1089/thy.2023.0141. View source
- Ringel MD, Sosa JA, Baloch Z, et al. 2025 American Thyroid Association management guidelines for adult patients with differentiated thyroid cancer. Thyroid. 2025;35(8):841–985. doi:10.1177/10507256251363120. View source
Guidelines are updated over time. Links point to the publisher or DOI record; always check for the newest version.