Table 1. Well-differentiated thyroid carcinoma of low, middle, and intermediate risk, as classified by the ATA and BTA (American Thyroid Association, British Thyroid Association). The ATA and BTA categories are identical, except where additional BTA criteria are noted in red (from [10, 11]).

Risk	pTN	Further features
Low	pT1a solitary or multiple N0/Nx pT1b N0/Nx pT2 N0/Nx pT3 > 4 cm N0/Nx	< 4 cm intrathyroid R0, R1 M0
Middle	pT3 N0 Nx pT3 N1a or N1b	in case of spread beyond the thyroid: microscopic R0 M0
High	pT4 M1 R2