LOW-PREVALENCE OF THE RET PTC3R1 REARRANGEMENT IN A SERIES OF PAPILLARY THYROID CARCINOMAS PRESENTING IN BYELARUS 10 YEARS POST-CHERNOBYL/

After the Chernobyl accident in 1986, there was a significant increase in the incidence of papillary thyroid cancer in fallout-exposed child ren from Belarus. Radiation-induced rearrangements of chromosome 10 in volving the c-ret proto-oncogene have been implicated in the pathogene sis of these cancers. The ret/PTC3r1 rearrangement was the most preval ent molecular lesion identified in post-Chernobyl papillary thyroid ca ncers arising in 1991 and 1992. We identified the ret/PTC1 rearrangeme nt in 29% of 31 papillary thyroid cancers presenting in Belarus in 199 6. In the present report, we examined 14 cases from this series (plus 1 additional case) and found a ret/PTC3r1 rearrangement in only 1 (7%) . The prevalence of ret/PTC3r1 in this series is significantly lower t han previously reported (p = 0.0006, Fisher exact test). This result s uggests a switch in the ratio of ret/PTC3 to ret/PTC1 rearrangements i n late (1996) versus early (1991-1992) post-Chernobyl papillary thyroi d cancers.