Thyroid cancer in adolescents and young adults: a population-based study in 185 countries worldwide

A new study led by scientists from the International Agency for Research on Cancer (IARC), in collaboration with researchers in Italy and China, provides the first comprehensive global assessment of the thyroid cancer burden among adolescents and young adults (AYAs) aged 15–39 years and suggests that overdiagnosis is the main driver of the observed increase in incidence of this disease. The study, published today in The Lancet Diabetes & Endocrinology, examined data from 185 countries worldwide.

Thyroid cancer has become one of the most commonly diagnosed cancer types in young people, particularly among young women. Using data from the Cancer Incidence in Five Continents Plus database and the World Health Organization (WHO) Mortality Database, the researchers found that thyroid cancer incidence rates among AYAs have increased rapidly since the 2000s in most countries, whereas thyroid cancer mortality rates have remained very low and stable.

The fastest increases in incidence were observed in China, Cyprus, Ecuador, the Republic of Korea, and Türkiye, where the average annual increases exceeded 10% in some cases. In 2022, thyroid cancer accounted for more than 237 000 new cases and 2100 deaths worldwide. It ranked among the top three most diagnosed cancer types among female AYAs in 100 countries and among male AYAs in 26 countries whereas thyroid cancer mortality rates were very low.

The study revealed a strong positive correlation between thyroid cancer incidence rates among AYAs and Human Development Index (HDI) level, suggesting that greater access to medical imaging and diagnostic procedures in more developed settings may have contributed to the increase. In contrast, thyroid cancer mortality rates among AYAs were low and relatively uniform across countries with different HDI levels.

“The epidemiological profile of thyroid cancer among young adults points to a large expansion of overdiagnosis to younger populations,” says Dr Salvatore Vaccarella, a scientist in the Cancer Surveillance Branch at IARC and the senior author of the study. Overdiagnosis can lead to aggressive treatments, physical and psychological harms, and financial burdens for individuals and health-care systems.

The study highlights that the impact of overdiagnosis is particularly severe among AYAs, compared with older adults. Besides physical harms and potential complications from surgery or radioactive iodine treatment, this age group faces unique psychological, social, and developmental challenges. AYAs are more likely to be uninsured, and young cancer survivors are more likely to experience workplace discrimination or encounter legal and social difficulties. Cancer diagnosis at this life stage can interrupt education, employment, and social maturation, compounding the financial and emotional burden.

“This study underlines the global relevance and rapid expansion of thyroid cancer overdiagnosis, especially in countries undergoing economic transition,” adds Dr Vaccarella. “This emerging global public health challenge needs to be urgently addressed.”

Li M, Dal Maso L, Pizzato M, Rumgay H, Vaccarella S
Thyroid cancer in adolescents and young adults: a population-based study in 185 countries worldwide
Lancet Diabetes Endocrinol. Published online 17 November 2025;
https://doi.org/10.1016/S2213-8587(25)00289-X

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