Thyroid carcinoma in children and adolescents resulting from the Chernobyl accident: possible causes of the incidence increase overestimation.

The Chernobyl accident in the nuclear power plant on 26th April 1986 was followed by numerous publications overestimating the medical consequences of the disaster. In the publications, interpretations of spontaneous diseases as radiation-induced, indication of radioactivity or dose levels without confrontation with the natural radiation background, or conclusions about incidence increase without comparison with the increase tendencies in larger regions or the whole country, can be found. Improved diagnostics after the Chernobyl accident is not always taken into account. The high figures could have been caused in some cases by non-random material selection or inadequate morphological assessment of biopsy specimens. The application of the linear-no-threshold theory to the inhabitants of contaminated areas contributed to an overestimation of medical consequences of the Chernobyl accident as well. The incidence increase of thyroid carcinoma in children and adolescents started in 1990, four years after the accident. High tumor expectancy after the accident, in the circumstances of limited technical possibilities and outdated equipment of histological laboratories, contributed to a higher number of registered cases. The quality of specimens necessary for the assessment of nuclear criteria of papillary carcinoma was not always achieved at that time. The incidence increase of thyroid carcinoma can, at least in part, be explained by improved detection of thyroid nodules with occasional false-positive conclusions about malignancy. Besides, latent carcinomas and well-differentiated thyroid tumors of uncertain malignant potential, diagnosed as malignancies, could have additionally contributed to the high figures.