Clonality of thyroid nodules in XXXX .

@entity1 @entity1377 @entity1354 @entity5 @entity1373 @entity4913 @entity189 @entity5651 @entity259
Clonality studies have suggested that @entity5 are monoclonal and @entity1373 are polyclonal. To investigate this question in thyroid, we analyzed the clonality of 26 morphologically characterized hyperplastic nodules from 19 @entity1 with @entity5651 . For comparison we studied six @entity259 . We used the highly informative M27 beta probe that maps to the X-chromosome DXS255 locus (X cen- @entity1354 .22). Material was obtained from 52 nodules; tissue from nine nodules was rejected because of contamination with normal elements, five @entity1 (eight nodules) were homozygous at @entity4913 I sites in nonnodular thyroid tissue, and three nodules were excluded for technical reasons. Methylation patterns after Hpa II digestion confirmed polyclonality in all nontumorous thyroids of informative @entity1 . Seven hyperplastic nodules were polyclonal, and 18 were monoclonal; one showed loss of heterozygosity. One nodule exhibited aberrant methylation. Multiple nodules were obtained from four @entity1 ; in three, all were monoclonal with activation of the same allele. Three @entity1377 were monoclonal; two exhibited aberrant methylation. One @entity189 showed loss of heterozygosity. Our data indicate that morphologically indistinguishable hyperplastic thyroid nodules may be monoclonal or polyclonal. These findings suggest that variable molecular mechanisms are involved in the pathogenesis of nodules in @entity5651 . Future studies will need to explore the biological significance of nodules of variable clonal origin.
