Pathology of Radiation-Induced Thyroid Cancer: Lessons from Chernobyl Thyroid Cancer Study

This chapter analyzes histopathological characteristics of papillary thyroid carcinoma (PTC) in subjects of Ukraine who were children and adolescents at the time of the Chernobyl accident. Tumor architecture and invasive properties significantly changed with patients’ age at surgery increasing from 4 to 48 years and with the time elapsed after the accident extending to 30 years. Two major linear trends, the age- and time-related, were revealed for most pathological characteristics; some of them were ascending and some descending. “Radiogenic” PTC in subjects aged ≤4 years at the time of exposure who resided in three regions most contaminated by 131I differed from “sporadic” PTC in age-matched groups of patients from the same regions in terms of both tumor histoarchitectonics and invasiveness. “Radiogenic” PTC displayed a higher frequency of invasive features especially pronounced in children and adolescents. Changes in histopathological characteristics suggest that the phenotype of both “radiogenic” and “sporadic” PTCs becomes less invasive at older patients’ ages. The frequency of intermediate pathological diagnoses of thyroid tumors according to the WHO Classification of Tumours of Endocrine Organs, 4th edition, in the Ukrainian cases included in the Chernobyl Tissue Bank appeared to be not more than 3%.