High prevalence of RET/PTC rearrangements in Ukrainian and Belarussian post-Chernobyl thyroid papillary carcinomas: A strong correlation between RET/PTC3 and the solid-follicular variant

A sharp increase in the incidence of pediatric thyroid papillary cancer was documented after the Chernobyl power plant explosion. An increased prevale nce of rearrangements of the RET protooncogene (RET/PTC rearrangements) has been reported in Belarussian post-Chernobyl papillary carcinomas arising b etween 1990 and 1995. We analyzed 67 post-Chernobyl pediatric papillary car cinomas arising in 1995-1997 for RET/PTC activation: 28 were from Ukraine a nd 39 were from Belarus. The study, conducted by a combined immunohistochem istry and RT-PCR approach, demonstrated a high frequency (60.7% of the Ukra inian and 51.3% of the Belarussian cases) of RET/PTC activation. A strong c orrelation was observed between the solid-follicular subtype of papillary c arcinoma and the RET/PTC3 isoform: 19 of the 24 RET/PTC-positive solid-foll icular carcinomas harbored a RET/PTC3 rearrangement, whereas only 5 had a R ET/PTC1 rearrangement. Taken together these results support the concept tha t RET/PTC activation plays a central role in the pathogenesis of thyroid pa pillary carcinomas in both Ukraine and Belarus after the Chernobyl accident .