Low frequency of numerical chromosomal aberrations in follicular thyroid tumors detected by comparative genomic...

Follicular thyroid tumors vary from adenomas to widely invasive carcinomas, and a stepwise progression from normal thyrocyte to malignant tumor has been suggested to be due to an accumulation of genetic alterations. We have used comparative genomic hybridization to screen 21 follicular thyroid tumors (8 adenomas and 13 carcinomas) for gains and losses of DNA sequence copy numbers. In general, the tumors showed few alterations involving several different chromosomal regions. The frequency of alterations was similar in the benign (mean, 1.9) and malignant (mean, 1.5) tumors, as well as in minimally (mean, 1.5) and widely invasive carcinomas (mean, 1.6). However, specific loss of 9q13-q21.3 was detected in three tumors, which were all carcinomas showing oxyphilic changes (Hürthle cell carcinomas; P = 0.003). The fact that DNA copy number alterations were found with a similarly low frequency in both benign and malignant follicular thyroid tumors does not support the hypothesis of a multistep tumor progression in these tumors. Genes Chromosomes Cancer 25:349-353, 1999.