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Title: Histopathological features of papillary thyroid carcinomas detected during four screening examinations of a Ukrainian-American cohort.
Authors: Bogdanova TI,  Zurnadzhy LY,  Nikiforov YE,  Leeman-Neill RJ,  Tronko MD,  Chanock S,  Mabuchi K,  Likhtarov IA,  Kovgan LM,  Drozdovitch V,  Little MP,  Hatch M,  Zablotska LB,  Shpak VM,  McConnell RJ,  Brenner AV
Journal: Br J Cancer
Date: 2015 Dec 1
Branches: LGS, OD, REB
PubMed ID: 26625214
PMC ID: PMC4705885
Abstract: BACKGROUND: There are limited data on the histopathology of papillary thyroid carcinomas (PTCs) diagnosed in irradiated populations. We evaluated the associations between iodine-131 dose and the histopathological characteristics of post-Chernobyl PTCs, the changes in these characteristics over time, and their associations with selected somatic mutations. METHODS: This study included 115 PTCs diagnosed in a Ukrainian-American cohort (n=13,243) during prescreening and four successive thyroid screenings. Of these PTCs, 65 were subjected to somatic mutation profiling. All individuals were <18 years at the time of the Chernobyl accident and had direct thyroid radioactivity measurements. Statistical analyses included multivariate linear and logistic regression. RESULTS: We identified a borderline significant linear-quadratic association (P=0.063) between iodine-131 dose and overall tumour invasiveness (presence of extrathyroidal extension, lymphatic/vascular invasion, and regional or distant metastases). Irrespective of dose, tumours with chromosomal rearrangements were more likely to have lymphatic/vascular invasion than tumours without chromosomal rearrangements (P=0.020) or tumours with BRAF or RAS point mutations (P=0.008). Controlling for age, there were significant time trends in decreasing tumour size (P<0.001), the extent of lymphatic/vascular invasion (P=0.005), and overall invasiveness (P=0.026). CONCLUSIONS: We determined that the invasive properties of PTCs that develop in iodine-131-exposed children may be associated with radiation dose. In addition, based on a subset of cases, tumours with chromosomal rearrangements appear to have a more invasive phenotype. The increase in small, less invasive PTCs over time is a consequence of repeated screening examinations.