Thyroid cancer is classified into four types: papillary, follicular, medullary and anaplastic. Papillary and follicular neoplasm of the thyroid are commonly referred to as differentiated thyroid cancers (DTC). This article outlines factors affecting the incidence, management and prognosis of DTC.
What is Thyroid Cancer ?
The thyroid gland is located at the base of the throat and consists of two lobes either side of the windpipe. It produces the hormones triiodothyronine, thyroxine and calcitonin which have important effects on metabolic rate and blood calcium levels.
Cancer of the thyroid is relatively rare. In the UK for example, thyroid malignancy accounts for around 1% of all cancer cases. Worldwide the rate of thyroid carcinoma has risen over the last 25 years. It is unclear whether this is a true rise in incidence, or due to increased diagnosis. The incidence of thyroid cancer is higher in women than men and most patients are 30-50 years old at diagnosis.The most common sign of thyroid cancer is a painless swelling in the throat.
The cause of thyroid malignancy is largely unclear, although exposure to ionising radiation (particularly during childhood) has been shown to be the cause in a minority of cases. Atomic bombs detonated over Hiroshima and Nagasaki in 1945 and the Chernobyl nuclear reactor accident in 1986 exposed some people to high levels of ionising radiation, leading to an increased incidence in the disease.
Papillary and Follicular Neoplasm of the Thyroid
Differentiated thyroid cancers (DTCs) tend not to run in families and are less aggressive than medullary or anaplastic thyroid cancers. Papillary carcinoma is the most common type of thyroid malignancy, accounting for around 80% of thyroid cancers. It is most common in people under 40, especially women. Follicular neoplasm of the thyroid is much less common, accounting for only 10% of thyroid cancers. Follicular thyroid malignancy tends to affect older adults.
The prognosis (outlook) for patients with papillary or follicular thyroid cancer is good, since these tumors tend to grow slowly and are relatively easy to treat. Children with differentiated thyroid malignancy tend to present with a greater spread of disease than adult patients and have a high chance of recurrence, but still have a favourable prognosis. The primary treatment for DTC is surgical removal of thyroid tissue.
Radioactive iodine (RAI) may be used post surgery to kill remaining malignant cells. However, RAI use should be carefully considered after assessing the relative risks and benefits, since it may be associated with a risk of second malignancies. The aggressiveness of the initial disease and the chance of recurrence are primary factors in the decision to use RAI.
Follow-up post treatment should be lifelong, however the frequency of check ups usually decrease with time as patients are found to be disease-free. Following treatment, 80-90% of DTC patients have a normal life expectancy.
United Kingdom National Health Service website: wwww.nhs.uk
Initial management and follow-up of differentiated thyroid cancer in children. S.Waguespack & G.Francis. Journal of the National Comprehensive Cancer Network, 2010, Vol 8, P1289-300.