Monosomy and ring chromosome 13 in a thyroid nodular goiter-do we underestimate its relevance in benign thyroid lesions?

Classical cytogenetic examination of a thyroid nodular goiter revealed the existence of two different cytogenetically aberrant cell clones. They were characterized by monosomy 13 as the sole abnormality in one clone, and loss of one chromosome 13 and a ring chromosome that was found to consist of chromosome 13 material by fluorescence in situ hybridization in the other clone. We have concluded that during the course of karyotypic evolution, the instability of the ring chromosome has led to its loss and subsequent monosomy 13. In the literature, two cases of partial monosomy 13 have been reported in adenomatous goiters, suggesting that this abnormality characterizes a rare but distinct subgroup of benign thyroid lesions histologically presenting as adenomatous goiters. Possible target genes of these deletions are the retinoblastoma (RB1) gene locus and the MIR16-1/15A cluster. Based on similar changes in other tumors, it seems reasonable to also analyze a large number of adenomatous goiters for submicroscopic deletions of the long arm of chromosome 13.