Taking in consideration the data on the progression of WDTC (no p53 mutations) to PDTC and UTC, which frequently harbour p53 inactivation, gross genetic alterations and aneuploidy, it is likely that in the more advanced steps of progression, p53 inactivation (“suppressor pathway”) represents the most frequent mechanism of chromosome instability in thyroid cancer. This evidence concerns the gene TP53 and thyroid gland carcinoma.