Histopathological analysis of papillary thyroid carcinoma detected during ultrasound screening examinations in Fukushima

Abstract

Thyroid ultrasound screening of young residents in Fukushima prefecture of Japan demonstrated high detection rate of papillary thyroid carcinoma (PTC). Detailed morphological analysis of these tumors was not presented to date. This study sets out to evaluate changes in histopathological and invasive characteristics of Fukushima PTC with time after the nuclear accident of March 2011 in all available cases and in different age subgroups. Histological specimens of 115 PTCs from patients aged ≤ 18 years at the time of Fukushima Dai‐ichi Nuclear Power Plant accident operated at Fukushima Medical University during 2012‐2016 were reviewed. Patients were divided into those treated during the first 4 years after the accident (n=78, shorter‐onset) or later (n=37, longer‐onset). The whole group and three age subgroups: children (aged < 15 years), adolescents (aged from 15 to < 19 years), and young adults (aged from 19 years) at surgery were analyzed. No statistically significant time‐related changes in tumor structure and invasiveness were found in the whole group or in age‐matched subgroups. Statistically significant age‐related downtrend was observed for intrathyroid spread in the whole group of patients. The absence of temporal changes in tumor morphological characteristics and tumor invasiveness strongly suggests common etiology of the shorter‐ and longer‐onset Fukushima PTCs, which are unlikely related to the effect of exposure to very low doses of radiation.

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