What is papillary thyroid microcarcinoma?
Papillary thyroid microcarcinoma (PTMC) is defined as a papillary thyroid carcinoma less than or equal to 10 mm in size.
What is the natural history of PTMC?
The prognosis for PTMC is very good.
How is PTMC diagnosed?
PTMC is usually asymptomatic. It is usually detected initially on an ultrasound scan of the thyroid, which may lead to an ultrasound-guided FNA of a suspicious-looking thyroid nodule. Sometimes it is detected incidentally when other imaging is requested. Patients sometimes have their initial studies overseas and then may seek medical advice when they return to New Zealand.
How is PTMC treated?
First, it is important to exclude any adverse features – extrathyroidal extension or lymph node metastases – with an ultrasound scan of the neck; although uncommon, this sometimes does occur.
There are three ways of treating PTMC: Active surveillance, surgery or ultrasound-guided ablation, and each method has its pros and cons.
What is active surveillance?
Active surveillance involves performing regular ultrasound scans of the thyroid and the neck, initially every six months and then every year to detect any significant growth (>3mm) of the PTMC or lymph node involvement. The purpose of active surveillance is not to prevent progression but to prevent unfavourable events associated with tumour progression. If the tumour progresses, then the patient is offered either surgery or radiofrequency ablation (RFA). It is also important that patients who opt for active surveillance are motivated to avoid intervention and to have annual ultrasounds. They need to accept that they have a small cancer, and although there is a small chance of progression of their cancer, they are very unlikely to come to any serious harm.
Which patients are suitable for active surveillance?
The ideal patients for active surveillance of PTMC are patients over the age of 60 years (as their tumours have the lowest rates of growth) and with tumours that are not abutting the trachea, the common carotid artery or the recurrent laryngeal nerve (RLN). Patients with PTMC adjacent to the trachea or RLN and patients with nodal metastasis are not suitable for active surveillance. Ito observed that patients younger than 40 years had a progression rate of 8.9%, whereas it was 3.5% in patients between 40 and 60 years, and 1.6% in patients older than 60 years.
Tuttle et al. found that individuals diagnosed under 50 years of age had a nearly fivefold higher risk of tumour progression than individuals age 50 years or older (27.3% vs 4.6% at five years).
The 2025 American Thyroid Association guidelines for the management of differentiated thyroid carcinoma states that, “Active surveillance may be offered as an appropriate management option for some patients with cT1aN0M0 PTCs (PTMC)”.
What is the evidence for active surveillance?
Ito reported on 3222 carefully selected patients with PTMC managed with active surveillance at Kuma Hospital. He showed that 6.6% had tumour progression, 1.6% had cervical node metastases and one patient had distant metastasis by 20 years. No patients died of PTMC.
Which patients with PTMC are better treated with surgery?
Patients with PTMC with any of the contraindications for active surveillance: age <20, nodal metastases, tumour adjacent the recurrent laryngeal nerve or tumour abutting the trachea along a broad front are good candidates for surgery. Usually, a hemithyroidectomy is appropriate. Radioactive iodine is usually not required unless there is significant lymph node involvement.
What about radiofrequency ablation for PTMC?
The 2025 American Thyroid Association guidelines for the management of differentiated thyroid carcinoma states that, “ultrasound-guided percutaneous ablation (RFA) may be considered as an alternative to active surveillance or resection (surgery) for cT1aN0M0 PTC in selected patients”.
In 2025 Jeong, et al. reported on 65 patients with PTMC treated with RFA and followed for a median of 10 years. He noted no local, nodal or distant recurrences. Five (8%) patients developed new primaries, four of which were treated with RFA and one treated with surgery.
Cho, et al. in a meta-analysis of five-year follow-up results of thermal ablation for low-risk PTMC, reported there was no local tumour recurrence, lymph node metastasis, distant metastasis, or conversion surgery in 207 patients with PTMC.
Summary
PTMC has an excellent prognosis. Active surveillance, surgery or radiofrequency ablation are all approved treatment options, with the choice of treatment depending on the clinical situation.
References
1. Ringel MD, Sosa JA, Baloch Z, Bischoff L, Bloom G, Brent GA, et al. 2025 American Thyroid Association management guidelines for adult patients with differentiated thyroid cancer. Thyroid 2025 Aug; 35(8):841–985.
2. Ito Y, Miyauchi A, Kihara M, Higashiyama T, Kobayashi K, Miya A. Patient age is significantly related to the progression of papillary microcarcinoma of the thyroid under observation. Thyroid. 2014 Jan;24(1):27-34. doi: 10.1089/thy.2013.0367.
3. Tuttle RM, Fagin JA, Minkowitz G, Wong RJ, Roman B, Patel S, et al. Natural history and tumor volume kinetics of papil¬lary thyroid cancers during active surveillance. JAMA Otolaryn¬gol Head Neck Surg. 2017 Oct 1;143(10):1015-1020. doi: 10.1001/jamaoto.2017.1442.
4. Jeong SY, Baek SM, Shin S, Son JM, Kim H, Baek JH. Radiofrequency ablation of low-risk papillary thyroid microcarcinoma: A retrospective cohort study including patients with
more than 10 years of follow-up. Thyroid. 2025 Feb;35(2):143-152. doi:10.1089/thy.2024.0535.
5. Cho SJ, Baek SM, Na DG, Lee KD, Shong YK, Baek JH. Five-year follow-up results of thermal ablation for low-risk papillary thyroid microcarcinomas: systematic review and meta-analysis. Eur Radiol. 2021Sep;31(9):6446-6456. doi: 10.1007/s00330-021-07808-x. Epub 2021 Mar 13. PMID: 33713168.
