Four years after the Fukushima accident, TC screening data from the first and second round (up to December 2014) were compared with the Japanese nationwide annual TC incidence, and with the incidence in one area of Fukushima prefecture selected as reference (Tsuda et al., 2016). The authors reported that the observed number of TCs was substantially higher than the expected number based on national and regional incidence data, and concluded that this increase could be attributed to ionizing radiation exposure from the accident. This ecological study has been strongly criticized by scientists around the world because of serious methodology limitations; further, the study conclusions are not supported by the results (Davis, 2016, Jorgensen, 2016, Korblein, 2016, Shibata, 2016, Suzuki, 2016, Takahashi et al., 2016, Takamura, 2016, Wakeford et al., 2016). Limitations of ecological study design are well-known, although the authors did not acknowledge the issue of ecologic fallacy. Another criticism was that the data from the Fukushima screening program are not directly comparable with the cancer registry data from the rest of Japan where systematic advanced ultrasound technology is not used to detect cases. The authors of these criticisms suggested that though the increased TC number could be associated with the exposure from radioactive fallout, a more plausible conclusion would be that the screening program is finding an anticipated increase in TC detection across the Fukushima prefecture. Indeed, Tsuda and colleagues did not consider the latent properties of TC, nor the fact that a prevalent cancer detected by screening might have had first preclinical manifestations of abnormality before the nuclear accident.Thereafter, several researchers have analysed the relationship between radiation exposure (with different estimated exposure levels, mostly using an external dose) and TC prevalence and incidence in residents aged ≤18 years in the Fukushima prefecture at time of the disaster (Kato, 2019, Nakaya et al., 2018, Ohira et al., 2019a, Ohira et al., 2020, Ohira et al., 2019b, Ohira et al., 2016, Ohira et al., 2018, Suzuki et al., 2016, Toki et al., 2020, Yamamoto et al., 2019), but no radiation-related risks have been demonstrated to date.