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149chap.IIIStruggle Against RadioactivityFUKUSHIMA: Lives on the LineTable 2. Results of Thyroid Screening in 2011 (as of March 31, 2012)Total number of participants38,114 peopleExamination resultClassificationNumber of people (person)Rate (%)Class A(A1)No nodule or cyst24,468 participants64.2%99.5%(A2)Nodules ≤5.0 mm or cysts ≤20.0 mm 13,460 participants35.3%Class BNodules ≥5.1 mm or cysts ≥20.1 mm186 participants0.5%Class CImmediate secondary examination required based on thyroid condition0 participants0%[Screening result classification]• Those with A1 and A2 results will be followed up at the next examination (2014 onward)• hose with B or C results will undergo a secondary examination (the timing and location of the secondary examination will be notified)*Some of the A2 results are classified as B when clinically indicated based on the thyroid condition(Reference)Examination resultsNumber of participants (person)Rate (%)TotalWith nodules≥5.1 mm184 participants0.48%386 participants (1.0%)≤5.0 mm202 participants0.52%With cysts≥20.1 mm1 participant0.002%13,380 participants (35.1%)≤20.0 mm13,379 participants35.10%*Mixed cystic-solid nodules were also observedand urine tests, and if clinically indicated on the basis of our criteria, fine-needle aspiration cytology will be performed to determine if the lesion is benign or malignant. Therefore, it is expected that many cases will require no cytology examination following the ultrasound screening. Depending on the individual result, the residents in class B may have different recommendations, such as a usual re-screening after 2.5 years similar to that in class A, a follow-up screening in a few months to a year, cytology examinations, or a surgical treatment.Classification of the Thyroid Ultrasound Examination ResultsTable 2 shows results of 38,114 participants, who underwent thyroid examination by the end of March 2012. Only 186 or 0.5% of the participants were classified as class B, which requires a secondary examination. None were classified as class C, in which lesions were suspected to be malignant and required immediate re-examination. Most participants were classified as A1 or A2, who were recommended a routine re-screening after 2.5 years. Approximately 30% of them were classified as A2. The findings of A2 results are generally a small nodule or a colloid cyst without nodular components, which are so insignificant that those participants are often not even referred to specialists in the routine clinical setting. Most are cysts, and >90% of them are multiple cysts of ≤5 mm. Only 0.5% had nodules of ≤5 mm, which are difficult to differentiate from cysts and are considered benign. All of these cases were re-examined by a specialist, and if malignancy was strongly suspected despite its small size of ≤5 mm, or if the routine re-examination in 2.5 years appeared to be too delayed, they were classified as B. There was one such case. Secondary ExaminationThe external expert committee advised that the facility to be used for the secondary examinations should have a medical specialist of the Japan Thyroid Association, the Japan Association of Endocrine Surgeons, or the Japanese Society of Thyroid Surgery, and a medical specialist of the Japan Society of Ultrasound in Medicine (a body surface/general medical specialist). Because the secondary examination is currently applicable for only 0.5% of the participants, it has been undertaken at the Fukushima Medical

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