Thyroid carcinoma in children, adolescents, and young adults in Brazil: A report from 11 population-based cancer registries.

Rates of thyroid cancer, particularly the papillary subtype, are steadily increasing in children and AYAs, especially among females. There are variations among geographic areas. This increased incidence is unlikely to be explained by screening, as children less than 14 years of age do not typically undergo medical surveillance. Environmental risk factors must be investigated.