A hypothesis is proposed here that RET rearrangements in papillary thyroid cancers are related to the disease duration and tumor progression. The most common RET rearrangements are RET/PTC1 and RET/PTC3. RET/PTC1 is more prevalent in classic papillary thyroid carcinoma (PTC), its diffuse sclerosing variant, and papillary microcarcinoma; while RET/PTC3 is frequently found in less differentiated solid PTC. RET/PTC3 is associated with larger tumor size and multifocality in sporadic pediatric PTC. The RET rearrangements; especially RET/PTC3, which is frequently detected among Chernobyl thyroid cancers is developed after exposure to radiation at an early age, is proposed to be a potential trigger of malignancy. There are many late-stage tumors among the first-wave Chernobyl PTCs that tend to be larger and less differentiated than those detected later. The high proportion of late-stage cases shortly after the Accident is explained by the neglected cases in the screening process and also by the fact that some non-exposed patients were registered as radiation-exposed. The screening was productive because of the reservoir of undiagnosed cases in the population: registered incidence of thyroid cancer (TC) among children and adolescents prior to the Chernobyl disaster was low in the Soviet Union; compared to other developed countries. In conclusion, RET rearrangements, especially RET/PTC3, were correlated with the tumor progression. If the hypothesis defended here is correct, a low prevalence of RET/PTC3 among sporadic TC is circumstantial evidence of efficient cancer diagnosis and early detection.

Introduction: On the 25th anniversary of the Chernobyl power plant Accident, interest was rekindled by the recent Japan Nuclear disaster, and the medical consequences from the fall out are once again under scrutiny. In a Nuclear power plant, the fuel, is an isotope of either Uranium or Plutonium. In the event of an Accident, radioactive elements escape into the environment. By far the most dramatic Accidents occurred at the Chernobyl Nuclear power plant in 1986 and at the Fukushima Nuclear power plant of Japan on March 11, 2011. A major health hazard of a Nuclear Accident is childhood thyroid cancer which can be avoided if stable iodine is administered as prophylaxis during the hours immediately following the Accident and particularly in young children. Early administration of iodine is critical because it is not as useful if taken six hours after radiation exposure. Prior to 1986 the usefulness of this prophylaxis was controversial since there was limited data on is potential carcinogenic risks. At present, however there is no doubt that prophylaxis with potassium iodide (KI) with limited consumption of contaminated food is not harmful and useful if administered promptly.