Short-term cultures from 19 papillary thyroid adenocarcinomas revealed clonal numerical and/or structural chromosomal changes in 13 tumors, nonclonal abnormalities in one tumor, and only normal karyotypes in five tumors. Clonal abnormalities of chromosome 10 were present in three tumors, two of which had the translocation t(7;10)(q35;q21). Numerical abnormalities of chromosome 17 were detected in two tumors.