H³rthle thyroid tumors are characterized by frequent numerical chromosomal aberrations, including aneuploidy or polyploidy, losses and gains of some chromosomal regions and DNA fragmentation. In recent years, great attention has been paid to the combined analysis of morphologic and genetic features of oxyphilic tumors and to the elucidation of their pathogenesis. We analyzed for loss of heterozygosity (LOH) of the candidate regions for TCO (thyroid tumor with cell oxyphilia) and NMTC1 (nonmedullary thyroid carcinoma 1), 2 loci already mapped on chromosomes 19p13.2 and 2q21, respectively. Matched normal and tumor DNA samples from 70 patients with sporadic oxyphilic thyroid tumors and 20 with sporadic follicular tumors were subjected to microsatellite analysis using 10 markers on 19p13.2 and 6 markers on 2q21. This approach led us to the observation of a more significant LOH in oxyphilic than in follicular tumors. Allelic loss in tumor samples was evenly distributed in both 19p13.2 and 2q21 regions, in accordance with the established linkage of TCO and NMTC1 for inherited tumors. In order to investigate the possible contribution of both susceptibility loci in oxyphilic tumors, the family that led to the original mapping of TCO locus was reanalyzed for the markers in the 2q21 region. This led to the exclusion of linkage with the NMTC1 locus and to the refutation of the digenic inheritance hypothesis at least in this family.
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