Thyroid cancer is a rare and complex disease and the thyroid contains
various cell types from which specific diseases arise. The malignancie
s range from indolent to extremely aggressive. Several risk factors fo
r 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 pet possible to determine whether or not a specific cancer w
as induced by radiation and epidemiological studies therefore provide
the primary data on cancer risk in man after exposure to ionizing radi
ation. The current epidemiological knowledge on radiation-associated t
hyroid cancer is reviewed, focusing on the sharply increased risks rec
ently found among children in the Chernobyl area.