Thyroid Nodules · San Diego
How endocrinologists decide between watching a nodule, biopsy, radiofrequency ablation, or surgery: the ultrasound risk score, the size thresholds, and what biopsy results mean.
Thyroid nodules are very common. Many are found by chance on a CT scan, an MRI, or a carotid ultrasound done for another reason. Among nodules that are evaluated, roughly 7 to 15 out of 100 turn out to be cancer, and most of those are slow-growing papillary cancers with an excellent outlook.
The goal of a nodule evaluation is to find the small number that need treatment without putting everyone else through unnecessary biopsies or surgery. That decision rests on three things, in this order: a blood test, a careful ultrasound, and, only when the ultrasound calls for it, a fine-needle biopsy.
The first test is a TSH level. If TSH is low, the nodule may be producing thyroid hormone on its own (a "hot" or autonomous nodule). A thyroid uptake scan confirms this. Hot nodules are rarely cancerous and usually do not need a biopsy; they are treated if they cause hyperthyroidism or symptoms, with radioactive iodine, surgery, or in selected cases radiofrequency ablation.
If TSH is normal or high, the next step is a dedicated thyroid ultrasound.
Most U.S. radiologists and endocrinologists use the American College of Radiology TI-RADS system. Points are assigned for the nodule's composition, echogenicity, shape, margins and calcifications, and the total places the nodule in one of five categories. The category, combined with size, determines whether a biopsy is recommended.
| TI-RADS category | What it means | Biopsy (FNA) recommended at | Ultrasound follow-up at |
|---|---|---|---|
| TR1 | Benign | No biopsy | Not needed |
| TR2 | Not suspicious | No biopsy | Not needed |
| TR3 | Mildly suspicious | 2.5 cm or larger | 1.5 cm or larger |
| TR4 | Moderately suspicious | 1.5 cm or larger | 1.0 cm or larger |
| TR5 | Highly suspicious | 1.0 cm or larger | 0.5 cm or larger |
A worked example. A patient is told she has a "moderately suspicious" (TR4) nodule measuring 3.3 cm. Because a TR4 nodule of 1.5 cm or more meets the biopsy threshold, a fine-needle aspiration is recommended. The size alone does not mean cancer; it means the nodule has crossed the line where a biopsy gives useful information.
Nodules below the biopsy threshold but above the follow-up threshold are re-checked with ultrasound over time rather than biopsied immediately. Ultrasound quality matters: TI-RADS scoring depends on the person performing and reading the study, which is why we perform thyroid ultrasound ourselves rather than relying only on an outside report.
A fine-needle aspiration is done in the office under ultrasound guidance with a very thin needle, usually in a few minutes. The cells are classified using the Bethesda System, which has six categories.
| Bethesda category | Result | Usual next step |
|---|---|---|
| I | Nondiagnostic (not enough cells) | Repeat the biopsy under ultrasound |
| II | Benign | Ultrasound surveillance; treatment only if the nodule causes symptoms or grows (RFA is often an option) |
| III | Atypia of undetermined significance | Repeat biopsy and/or molecular testing; surveillance or surgery depending on results |
| IV | Follicular neoplasm | Molecular testing; diagnostic surgery is often recommended |
| V | Suspicious for malignancy | Surgical referral in most cases |
| VI | Malignant | Surgical referral; active surveillance can be an option for selected very small, low-risk papillary cancers |
Most benign nodules need nothing more than periodic ultrasound. Treatment makes sense when a benign nodule causes symptoms: pressure, difficulty swallowing, a visible lump, discomfort, or steady growth.
Watchful waiting. Appropriate for most small, symptom-free benign nodules. Follow-up ultrasound is typically repeated after one to two years, then at longer intervals if the nodule is stable.
Radiofrequency ablation (RFA). For a benign, symptomatic or cosmetically bothersome nodule, RFA shrinks the nodule in an office procedure under local anesthesia, with no incision and preservation of normal thyroid function in nearly all patients. It requires a benign biopsy result first. Read how RFA works and our results in 118 patients.
Ethanol ablation. For nodules that are mostly fluid (cysts) and keep refilling after drainage, injecting a small amount of alcohol is a simple, effective first option. More on ethanol ablation.
Surgery. Removing half or all of the thyroid remains the right choice for indeterminate or suspicious nodules, for very large or multinodular goiters extending into the chest, and for some patients who prefer it. See goiter treatment options.
Radioactive iodine. Used mainly for overactive (hot) nodules and toxic multinodular goiter.
Not by itself. Size determines whether a biopsy is worthwhile; the ultrasound features (TI-RADS category) say far more about cancer risk than size does.
This is uncommon. Follow-up ultrasound is done to catch the rare nodule that was misclassified or that changes, not because benign nodules routinely become malignant.
Thyroid guidelines generally define meaningful growth as an increase of at least 20% in two dimensions (with at least 2 mm of change) or more than 50% in volume. Smaller changes are often within measurement variation.
Routine thyroid hormone "suppression" therapy is not recommended for benign nodules in the U.S. The benefit is small and the risks to heart and bone are real.
Most patients describe a brief pressure sensation. A local anesthetic can be used, and you can return to normal activity the same day.
Tessler FN, et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. J Am Coll Radiol. 2017;14:587–595.
Haugen BR, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016;26:1–133.
Ali SZ, et al. The 2023 Bethesda System for Reporting Thyroid Cytopathology. Thyroid. 2023;33:1039–1044.
Written by Darius A. Schneider, MD, PhD, board-certified endocrinologist (ECNU-certified in neck ultrasound). Reviewed October 2026.
We perform thyroid ultrasound and ultrasound-guided biopsy in our office and will tell you plainly whether your nodule needs watching, a biopsy, or treatment.
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