After the Fukushima Daiichi Nuclear Power Plant accident that followed the Great East Japan Earthquake and tsunami on March 11, 2011, a large-scale thyroid ultrasound examination (TUE) survey began for people aged 18 years or younger at the time of the disaster. We would like to report the thyroid cancers screened from this survey.We analyzed clinicopathological findings of our operated 145 thyroid cancer.
Among these 145 subjects, 143 papillary thyroid carcinomas, one poorly differentiated thyroid carcinomas, and one other thyroid carcinoma were postoperatively confirmed. Mean age at diagnosis was 18 years, and mean tumor size was 15 mm.Even though the tumor smaller than 10mm, almost cases were not encapsulated PTC. There were no encapsulated cases smaller than 10mm without vascular/capsular invasion and lymph node metastasis. Extra thyroidal invasion and node positive were shown in 45% and 79%, postoperatively. Total thyroidectomy was performed in only 8% unlike Chernobyl. Our operated cases were not included super-low risk cases recommended active surveillance, and also included high risk cases only a little.Thyroid cancer detected in Fukushima does not display specific qualitative changes in tumor histopathology or morphological features of tumor aggressiveness over time unlike Chernobyl. Similarity of pathological characteristics between tumors removed within 4 years after the accident and 4-5 years after it strongly suggest their common etiology, which is unlikely related to radiation and also is in contrast to Chernobyl. Most cases were diagnosed with classical PTC, and there were few cases with solid variant PTC, unlike Chernobyl.Genetic alteration was also different between the children of Chernobyl and Fukushima.Fukushima PTC becomes less invasive at older ages which is similarly to ‘radiogenic’ and ‘sporadic’ PTC from Chernobyl.
Conclusively, we are aware of the high prevalence of thyroid cancer detected by sophisticated and large-scale ultrasound screenings following the accident.