Genome-wide copy number imbalances identified in familial and sporadic medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) is a malignant tumor of the calcitonin-secreting parafollicular C cells of the thyroid occurring sporadically and as a component of the multiple endocrine neoplasia type 2/familial medullary thyroid carcinoma syndrome. The primary genetic cause of multiple endocrine neoplasia type 2 is germline mutation of the RET protooncogene. Somatic point mutations in RET also occur in sporadic MTC. Although RET mutation is likely sufficient to cause C-cell hyperplasia, the precursor lesion to MTC, tumor progression is thought to be due to clonal expansion caused by the accumulation of somatic events. Using the genome-scanning technique comparative genomic hybridization, we identified chromosomal imbalances that occur in MTC including deletions of chromosomes 1p, 3q26.3-q27, 4, 9q13-q22, 13q, and 22q and amplifications of chromosome 19. These regions house known tumor suppressor genes as well as genes encoding subunits of the multicomponent complex of glycosylphosphatidylinositol-link...