PEDIATRIC THYROID-CANCER AFTER THE CHERNOBYL DISASTER - PATHOMORPHOLOGIC STUDY OF 84 CASES (1991-1992) FROM THE REPUBLIC OF BYELARUS

Background. During the initial period after the Chernobyl accident, la rge amounts of radioactive iodine were released in fallout, resulting in serious exposure to the thyroid gland in the residents of areas aro und the nuclear power station. Beginning in 1990, a definite increase in the incidence of thyroid cancer was noted in children of the Republ ic of Belarus. Methods. Morphologic and clinical features of 84 cases of post-Chernobyl thyroid carcinoma in Belarussian children from 5 to 14 years of age are reported. The latent period for tumor development was 4-6 years, with a mean of 5.8 years. Results. Papillary carcinoma was found in 83 patients and medullary carcinoma in one. Besides typic al papillary carcinoma (14%), solid (34%), follicular (33%), mixed (10 %), and diffuse sclerosing (9%) variants were observed. The follow-up period ranged from 8 months to 2.5 years. One patient died, local recu rrence developed in 2, and cervical lymph node metastases developed in 10. To date, the incidence of local recurrence or metastatic disease after surgery was significantly higher in patients 5-8 years of age an d in residents of areas nearest to the Chernobyl station. Conclusions. Post-Chernobyl pediatric thyroid carcinoma is characterized by a shor t latency, a higher proportion of tumors arising in young children, an d an almost equal sex ratio. Microscopically, these tumors were usuall y aggressive, often demonstrating intraglandular tumor dissemination ( 92%), thyroid capsular and adjacent soft tissue invasion (89%), and ce rvical lymph node metastases (88%). Papillary carcinoma was diagnosed in 99% of cases, with an unusually high frequency of solid growth patt erns. Morphologic changes in nonneoplastic thyroid tissue were present in 90% of the glands, and the most specific findings were vascular ch anges and perifollicular fibrosis.