- A papillary microcarcinoma is a papillary cancer of one centimeter or less, and it is common, grows very slowly and almost never puts life at risk.
- In very low-risk cases, the American guideline accepts active surveillance as an alternative to immediate surgery, and in the Japanese series, over ten years only 8 % grew and 3.8 % developed lymph node involvement.
- Surgery comes first when there are lymph nodes, the tumor is in contact with the trachea or the nerve, the biopsy suggests an aggressive subtype, or when the patient prefers not to live under surveillance.
The word cancer admits no sizes for the person receiving it. And yet, in the thyroid, size matters so much that those of one centimeter or less have their own category. They are detected more often because more ultrasounds are performed, and most of those detected would never have caused a symptom. From that observation came a strategy that thirty years ago seemed reckless and today is in the guidelines: monitoring them instead of operating.
What exactly it is
A A papillary thyroid cancer measuring one centimeter or less. It is the most frequent and the one with the best prognosis. is a papillary thyroid cancer measuring one centimeter or less in its largest diameter. Papillary is the most frequent type of all and the one with the best prognosis, and the «micro» only describes the size. Being small does not make it any less a cancer, but it does change what can be expected of it: it grows very slowly, and in the vast majority of cases it does not put life at risk, with or without treatment.
Active surveillance: what it is and where it comes from
A strategy of not operating at the outset and monitoring the tumor with periodic ultrasound, operating only if it grows or lymph nodes appear. does not mean forgoing treatment. It consists of not operating at the outset and, instead, performing an ultrasound every six or twelve months to check whether the tumor grows or lymph nodes appear, and operating only if that happens. It began in Japan, at Kuma Hospital, in 1993, and the largest published series has more than a thousand patients followed for years.
- 8 %of microcarcinomas grew by 3 mm or more over ten years of surveillance, in 1,235 patients followed without surgery.Ito Y et al. Thyroid. 2014, 24(1): 27-34.
- 3.8 %developed affected lymph nodes over ten years. None had distant metastasis or died of the tumor during observation.Same series. Those who progressed were operated on then.
When the answer is still surgery
Active surveillance is for a specific microcarcinoma, not for all of them. The Japanese consensus, from the group with the most experience in this strategy, specifies which ones are operated on from the start, and they are the same criteria applied at the consultation.
- When there are already affected lymph nodes in the neck or metastasis elsewhere.
- When the tumor is adherent to the trachea or lies along the path of the voice nerve, or has already affected the vocal cord.
- When the biopsy suggests an aggressive subtype, which is uncommon but exists.
- When the tumor grows or lymph nodes appear during surveillance.
- And when the patient, informed, prefers surgery to living with ongoing monitoring. It is as valid a reason as the others.
There is one more nuance, and it is about age: in the Japanese series, younger patients progressed more than older ones. A microcarcinoma in a thirty-year-old has many more decades ahead than one in a seventy-year-old, and that weighs in the decision.
And if it is operated on, how much is removed
When surgery is decided for a microcarcinoma without lymph nodes or extension outside the gland, the American guideline considers it sufficient to remove half of the thyroid gland, a Surgery in which half of the thyroid gland is removed. Also called hemithyroidectomy., unless there is a specific reason to remove the whole gland. The difference is not small: after removing only half of the gland, most people do not need to take hormone afterwards, and the risk to the voice and the parathyroids is on one side only, not both.
Active surveillance
- Ultrasound every six or twelve months, no surgery
- Surgery only if it grows or lymph nodes appear
- It avoids a scar, anesthesia and hormone replacement
- It requires consistency: the periodic check-ups are part of the strategy
Surgery
- Resolves it in a single procedure and allows the pathologist to study the whole tumor
- In most cases, removing half of the gland is enough
- A fine scar and, usually, one night in hospital
- It is the indicated option when there are lymph nodes, invasion or an aggressive subtype
Both are ways of treating the same tumor, and which one fits depends on the tumor, on age and on how you want to live the coming years.
What about ablation?
It is the question that comes right away, and it deserves an honest answer. Treating a cancer, even a small one, with heat instead of removing it has been studied mostly in Asia, and a recent international consensus contemplates it in very selected cases. It is not in the American or the Japanese guideline as a first-line option. At the clinic it is approached with that caution: for a microcarcinoma, the two paths with solid backing are monitoring or operating, and ablation is discussed only when neither is possible.
- Haugen BR et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016, 26(1): 1-133.
- 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, 24(1): 27-34.
- Sugitani I et al. Indications and Strategy for Active Surveillance of Adult Low-Risk Papillary Thyroid Microcarcinoma: Consensus Statements from the Japan Association of Endocrine Surgery Task Force. Thyroid. 2021, 31(2): 183-192.
- Zhao ZL et al. 2024 International Expert Consensus on US-guided Thermal Ablation for T1N0M0 Papillary Thyroid Cancer. Radiology. 2025, 315(1): e240347.
