Cancer of the thyroid, a small gland at the base of the neck, is uncommon and can occur at any age. It is most often diagnosed in people from their 20s through to their 60s. Almost all thyroid cancers (about 97%) are differentiated and have a good prognosis. When deaths do occur, they tend to arise from the spread of the cancer to the bones or lungs. There has been an increase of over 150% in the incidence of thyroid cancer in the UK over the past 30 years. It is unclear if this is because of more effective diagnosis or more people developing thyroid cancer. The rise in incidence has not been matched by a rise in mortality, but raises questions about assessment for people with suspected thyroid cancer and about appropriate treatment.
There is particular uncertainty about the management of nodules of small and intermediate size and classification, and practice varies internationally.
Thyroid cancer is usually treated by partial (hemi-) or total thyroidectomy, sometimes followed by radioactive iodine. Since thyroid cancer can occur in young adults and has a good prognosis, many who have this surgery will spend most of their lives without a thyroid gland. The long-term implications of this include lifelong treatment with replacement thyroid hormone, and possible complications such as hypoparathyroidism and vocal cord palsy. Internationally, very small thyroid tumours are sometimes managed with active surveillance.
Once thyroid cancer has been treated, there is still a chance it might recur. Recurrence is uncommon in well-differentiated cancers, but it can be more serious than the original occurrence. There are questions about the risk of recurrence and how this risk should be translated into a long-term follow-up strategy.