CDKN2B and thyroid cancer, nonmedullary, 2: This includes delineating type 1 ATC (BRAF-positive), likely originating from PTC; type 2 ATC (NRAS-positive), potentially originating from follicular thyroid cancer (FTC); type 3 ATC (mutated RAS-positive), potentially originating from FTC or Hürthle cell carcinoma; and a mixed ATC subtype characterized by inactive mutations in cell-cycle regulation genes (e.g., CDKN2A and CDKN2B).22