Active surveillance for small thyroid cancer
Active surveillance means watching a tiny, low-risk thyroid cancer with regular neck ultrasound instead of removing the gland straight away. Long-running Japanese programmes report that few of these tumours grow and nobody under watch has died of thyroid cancer, and the 2025 American guideline now lists it as an option, but only a conditional one resting on low-certainty evidence.
If a biopsy has shown a papillary thyroid cancer of 1 cm or less, with no spread to lymph nodes and no growth outside the gland, ask whether surveillance or needle ablation suits you before agreeing to surgery. It is a conversation to have with a specialist, not a foregone conclusion either way.
Why it exists
Most small thyroid cancers found today would never have caused harm. US papillary thyroid cancer diagnoses nearly quadrupled between 1975 and 2009, from 3.4 to 12.5 per 100,000, while deaths held at about 0.5 per 100,000.[1] Modelling estimates that 72–94% of US papillary thyroid cancers diagnosed between 1991 and 2019 were overdiagnoses: tumours that would never have caused symptoms.[2] The driver was high-resolution neck ultrasound and needle biopsy of nodules too small to feel.
Treating every one of those tumours has a price: removal of the thyroid, sometimes radioactive iodine, lifelong levothyroxine, and the surgical risks of a damaged voice nerve and permanently low calcium from injured parathyroid glands. Surveillance offers a way to keep the gland, and to avoid lifelong hormone replacement, for people whose tumour is unlikely to matter. The wider story of overdiagnosis is in Thyroid management and Cancer screening.
Who it is for
The 2025 American Thyroid Association guideline says active surveillance may be offered to selected patients with a papillary thyroid cancer of 1 cm or less, confirmed by biopsy, with no lymph-node spread and no growth beyond the thyroid. It is a conditional recommendation based on low-certainty evidence: a legitimate option to discuss, not a standard that overrides surgery. The same guideline says a needle biopsy is not routinely recommended for nodules of 1 cm or less that look low-risk on ultrasound.[3] The American guideline's discussion assumes a biopsy diagnosis; Korea's 2025 guideline makes it a requirement.[4]
What the long-term data show
The best data come from Kuma Hospital in Japan, which has offered surveillance since 1993; 3,222 adults chose it. About 5% of tumours had grown by 3 mm or more at 10 years (about 7% at 20), about 1–2% developed new lymph-node spread, roughly 1 in 8 people eventually chose or needed surgery, and nobody in the series died of thyroid cancer.[5] A 2025 review of surveillance at Kuma and a second Japanese hospital, running since 1995, likewise reports no thyroid-cancer deaths among patients under surveillance.[6]
These are self-selected patients looked at in hindsight, not randomised groups, which is why the recommendation stays conditional.
How surveillance works
The protocol is deliberately simple.
- Monitoring is by neck ultrasound, not blood tests. Routine thyroglobulin testing is not indicated.[7]
- Surgery has concrete triggers: the tumour grows by 3 mm or more or grows toward the back of the gland, a biopsy confirms new lymph-node spread, distant spread or growth outside the thyroid appears, or the patient becomes too anxious, can't keep up follow-up, or simply prefers surgery.[8]
The third route: ablation
The same guideline says ultrasound-guided ablation, usually with radiofrequency energy, may be considered for selected patients. It destroys the tumour through a needle without removing the gland. This is also a conditional recommendation: early results are good, but long-term data are thin and outcomes depend heavily on the operator's experience.[9][10]
What to do
- Don't ask for a "screening" thyroid ultrasound if you have no symptoms or specific risk factors.
- If a small nodule turns up, ask whether a biopsy is actually needed. For a low-risk nodule of 1 cm or less, usually not.
- If a biopsy shows a papillary cancer of 1 cm or less, confined to the gland, discuss surgery, surveillance and ablation with a specialist before deciding.
- On surveillance, keep the ultrasound appointments, and know the triggers that would change the plan.
Further reading
- Ringel MD et al. 2025 American Thyroid Association Management Guidelines for Adult Patients with Differentiated Thyroid Cancer. Thyroid 2025.[11]
- Miyauchi A et al. Long-Term Outcomes of Active Surveillance and Immediate Surgery for Adult Patients with Low-Risk Papillary Thyroid Microcarcinoma: 30-Year Experience. Thyroid 2023.[12]
- Ito Y et al. Active surveillance for small papillary thyroid carcinoma. Endocr Relat Cancer 2025.[13]
- Francis DO et al. Overdiagnosis of Papillary Thyroid Cancer. JAMA Netw Open 2026.[14]