Radiation-associated thyroid cancer--facts and fiction.

Thyroid cancer is a rare and complex disease and the thyroid contains various cell types from which specific diseases arise. The malignancies range from indolent to extremely aggressive. Several risk factors for thyroid cancers have been suggested, but only ionizing radiation has been found to have a causative effect. With the exception of tobacco, ionizing radiation is probably the most studied carcinogen there is. It is not yet possible to determine whether or not a specific cancer was induced by radiation and epidemiological studies therefore provide the primary data on cancer risk in man after exposure to ionizing radiation. The current epidemiological knowledge on radiation-associated thyroid cancer is reviewed, focusing on the sharply increased risks recently found among children in the Chernobyl area.