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Thyroid

Can a small thyroid cancer be watched instead of removed?

For one specific kind of small thyroid cancer, Korea now has a guideline that says yes, with conditions.

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Answer

For low-risk papillary thyroid microcarcinoma the Korean Thyroid Association's 2025 guideline permits active surveillance — monitoring rather than removing the tumour — in patients with no lymph node or distant metastasis, no gross extension beyond the thyroid, no invasion of the trachea or recurrent laryngeal nerve, and no aggressive histology.

Key takeaways

  • The Korean Thyroid Association published its first active surveillance guideline in June 2025, for adults with pathologically confirmed low-risk papillary thyroid microcarcinoma.
  • Surveillance is excluded if there is lymph node or distant metastasis, gross extrathyroidal extension, invasion of the trachea or recurrent laryngeal nerve, or aggressive histology.
  • Follow-up is neck ultrasound and thyroid function tests every six months for two years and annually thereafter, with surgery if the tumour grows significantly or new metastasis appears.
  • In pooled data on 9,397 patients, the disease progressed in 14.53 percent during surveillance and 14.91 percent went on to delayed surgery, with no thyroid cancer-related deaths in either the surveillance or the immediate surgery group.
  • Among 8,969 Korean patients with papillary thyroid microcarcinoma, 2 (0.02 percent) died of the cancer, while 1.2 percent died of something else.

Active surveillance means a cancer has been confirmed and a decision has been made not to remove it yet. It applies to one specific situation: papillary thyroid microcarcinoma, meaning a papillary thyroid cancer of 1 cm or less, judged low risk.

Who the guideline says it is for

The Korean Thyroid Association published the country's first guideline on this in June 2025. Surveillance is offered to adults with a pathologically confirmed Bethesda V–VI microcarcinoma and none of the following:

  • Clinical evidence of lymph node or distant metastasis.
  • Gross extension of the tumour beyond the thyroid.
  • Invasion of the trachea or the recurrent laryngeal nerve.
  • Aggressive histology.

Excluding those features requires high-resolution neck ultrasound performed by an experienced operator; contrast-enhanced neck computed tomography is optional. The guideline also asks that age, other illnesses and the patient's capacity for long-term follow-up be assessed before surveillance is chosen.

What surveillance involves

Neck ultrasound and thyroid function tests every six months for two years, then annually. Significant tumour growth, or newly detected lymph node or distant metastasis, is defined as progression and means surgery.

What the outcomes look like

Reported outcomes relevant to the decision
MeasureFigurePopulation
Died of the cancer0.02%8,969 Korean patients, 1994–2017
Died of any cause1.2%same cohort
Progressed during surveillance14.53%9,397 pooled patients
Went on to delayed surgery14.91%same pooled analysis
Thyroid cancer deaths during surveillanceNone recordedsame pooled analysis

The pooled analysis also found that patients who came to surgery after a period of surveillance had higher complication and recurrence rates than patients operated on immediately. How much of that is caused by the delay is unclear, because progression selects the tumours that were always going to behave worse — but it means surveillance is not free for the roughly one patient in seven who ends up in theatre anyway.

What this answer does not cover

  1. It applies only to papillary microcarcinoma judged low risk by the criteria above. A larger tumour, a different histology, or any of the excluded features is a different question with a different answer.
  2. Every published comparison of surveillance against immediate surgery is between patients who chose, not patients who were randomised.
  3. Whether surveillance is appropriate for a particular person is a decision for their clinician. This publication has no clinician on staff and does not offer clinical advice.

Sources

  1. 1

    Lee EK, Kim MJ, Kang SH, Koo BS, Kim K, Kim M, et al.

    2025 Korean Thyroid Association Clinical Management Guideline on Active Surveillance for Low-Risk Papillary Thyroid Carcinoma

    Endocrinology and Metabolism 2025;40(3):307-341

    doi:10.3803/enm.2025.2461 · PMID:40598902

    https://doi.org/10.3803/enm.2025.2461
  2. 2

    Nguyen VC, Song CM, Ji YB, Moon S, Park JH, Kim DS, Tae K

    Outcomes and effectiveness of active surveillance for low-risk papillary thyroid carcinoma: a systematic review and meta-analysis

    European Archives of Oto-Rhino-Laryngology 2025;282(5):2239-2252

    doi:10.1007/s00405-024-09141-7 · PMID:39668225

    https://doi.org/10.1007/s00405-024-09141-7
  3. 3

    Heo J, Ryu HJ, Park H, Kim TH, Kim SW, Oh YL, Chung JH

    Mortality rate and causes of death in papillary thyroid microcarcinoma

    Endocrine 2024;83(3):671-680

    doi:10.1007/s12020-023-03510-8 · PMID:37814113

    https://doi.org/10.1007/s12020-023-03510-8