RET and thyroid tumor: In this study, we used the array platform GeneChip Human Genome U133 Plus 2.0 (HG-U133 Plus 2.0) to analyse the expression of a wide range of genes (>30 000) in well- and poorly differentiated thyroid tumours and, to correlate, for the first time, gene expression with BRAF, RAS, RET/PTC and PAX8-PPARG alterations.