Short-term cultures from 38 follicular thyroid adenomas revealed clonal numerical and/or structural chromosomal changes in 8 tumors, nonclonal changes in 1 tumor, and only normal karyotypes in 29 tumors. Three cases had trisomy 22 as the sole anomaly. Two cases had a combination of trisomies for chromosomes 5, 7, 9, 12, and 16. (C) 1993 Wiley-Liss, Inc.