Pathology of thyroid cancer in children and adolescents of Ukraine having been exposed as a result of the Chernobyl accident

Abstract

Abstract. Pathology analysis of thyroid carcinomas removed in children and adolescents aged from 0 to 18 years at the time of the Chernobyl accident has been conducted in three age groups at the time of surgery (children aged up to 15, adolescents aged 15 to 18, and young adults aged 19 to 36 years) for three periods of observation: 1990–1995; 1996–2001; 2002–2004. In all age groups and for all periods of follow-up, papillary thyroid carcinomas (PTC) were predominant (> 90% of cases). A certain increase in the percentage of follicular carcinomas (FC) with increasing latency (time elapsed between surgery and Chernobyl accident) was noted. PTC were characterized by substantial changes in morphologic structure with increasing latency. The most aggressive PTC were reported in children operated on at the age of 4 to 14 years in 1990–1995 (shorter latency). With increasing latency an improvement of the character of biological behaviour of PTC was noted and confirmed by a decrease in the percentage of cases with extrathyroid spreading and presence of regional metastases. In patients born after the Chernobyl accident (1987 and later), as in children born before the accident, PTC were also prevalent, being characterized by marked invasive properties in cases of tumour size exceeding 1 cm. In addition, when compared with children born before the accident, a significantly higher percentage of FC was noted. Molecular-biology studies of PTC showed that RET rearrangements and BRAF mutations are closely related to tumour histological structure, latency, and patients' age at the time of surgery.