TP53 and thyroid cancer, nonmedullary, 2: The progression and dedifferentiation to PDTC and ATC are thought to arise from preexisting DTC as a result of acquiring additional genetic changes such as mutations in TERT promoter, TP53, EIF1AX, and CDKN2A.TP53 mutations are present in 50–80% of ATC and is one of the pivotal molecular alterations discriminating ATC from PTC or FTC (12).