Significance of trisomy 7 in thyroid tumors

Standard cytogenetic studies of a multifocal metastasizing papillary thyroid carcinoma revealed two clonal chromosome aberrations: rearranged 10q and trisomy 7. Trisomy 7 seemed to be restricted to tumor nodule A, whereas era (10q) was detected in tumor nodule B and in a metastatic lymph node. We applied fluorescent in situ hybridization to ask whether trisomy 7 was a feature of the original tumor nodule or an in vitro phenomenon changing quantitatively during early passages and to see whether trisomy 7 was restricted to tumor nodule A. We used the biotinylated chromosome 7 alpha-satellite probe D7Z1 on freshly dropped slides from metaphase harvests from tumor nodule A,B, and the lymph node and on touch preparations from the frozen specimen of tumor nodule A. Trisomy 7 was present in the original tumor nodule (6% of cells), as well as in early passages (P1-3) from both tumor nodules and the metastatic lymph node with a frequency of 10.7-13.2%. The detection of trisomy 7 as a stable component in short-term cell culture and its presence in the original tumor material indicates that this common numerical aberration is an in vivo phenomenon.