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According to the most recent estimates of the global cancer burden from the International Agency for Research on Cancer (IARC), in 2024 almost 1 million people were diagnosed with thyroid cancer and almost 50 000 people died from the disease. About three quarters of all new cases were diagnosed in women.
Thyroid cancer has become one of the most commonly diagnosed cancer types, particularly among young women. Known causes of thyroid cancer include exposure to radioiodines (including iodine-131) during childhood and adolescence, exposure to X-radiation, and exposure to gamma-radiation. However, previous IARC research has shown that this increase is driven largely by overdiagnosis, i.e. the diagnosis of a tumour that would not have progressed to cause symptoms or death in an individual’s lifetime. Overdiagnosis accounts for a large proportion of thyroid cancer diagnoses, up to 90% in some countries.
Greater access to medical imaging and diagnostic procedures and increased surveillance have contributed to this increase. Despite the large increase in incidence rates, thyroid cancer mortality rates have remained very low and stable. These findings indicate that overdiagnosis of thyroid cancer has become a major global health problem.
Overdiagnosis leads to overtreatment and exposes healthy individuals to unnecessary physical, psychological, and financial harms without improving health outcomes. For this reason, medical guidelines and experts worldwide recommend against screening people who have no symptoms of thyroid cancer.
During Thyroid Cancer Awareness Month 2026, IARC is highlighting the importance of avoiding unnecessary thyroid cancer screening in people without symptoms. Detecting cancers that would never have caused harm can lead to unnecessary treatment and lifelong consequences for patients. The goal should not be to detect more thyroid cancers but to detect the thyroid cancers that matter: those that require treatment and can threaten health.
