TABLE 3

Thyroid Cancer Risk Stratification

	ATA	Thyroid Cancer Risk Stratification	SNM
Very low risk		Unifocal or multifocal microcarcinomas (< 1cm)	√
		MACIS score < 6, or TNM score: T1–2, N0, M0	√
		In patients < 45 years old: tumors < 4 cm confined to the thyroid	√
		Excludes tumors with aggressive histology* or vascular invasion	√

Low-risk (all criteria must be met)		In patients < 45 years old: MACIS < 6, or TNM score: any T any N, M0	√
Low-risk (all criteria must be met)		In patients ≥ 45 years old: MACIS < 6, or TNM score: T2, N0, M0	√
	√	No local or distant metastases	√
	√	All macroscopic tumor has been resected	√
	√	There is no tumor invasion of locoregional tissues or structures	√
	√	The tumor does not have aggressive histology* or vascular invasion	√
	√	If ¹³¹I is given, there is no ¹³¹I uptake outside the thyroid bed on the first post-therapy scan	√

Intermediate/Moderate risk (any criteria)		In patients < 45 years old: tumors > 4 cm; macroscopic (> 1cm) N1a or N1b; T1–3, N1b, M0	√
		In patients ≥ 45 years old: T3, N0, M0 or T1–3, N1a, M0	√
		MACIS score > 6	√
		Minimally invasive (microscopic capsular, but not vascular invasion) FTC < 4 cm	√
	√	Tumor with aggressive histology* or vascular invasion	√
	√	Microscopic invasion of tumor into the perithyroidal soft tissues at initial surgery	√
	√	Cervical lymph node metastases, or ¹³¹I uptake outside the thyroid bed on the post-therapy scan

High-risk (any criteria)		In patients < 45 years old: T4a–4b, any N, M0, or any T, any N, M1	√
		In patients ≥ 45 years old: any T, N1a–1b, M0, AJCC Stages IVA, IVB, IVC	√
		FTC > 4 cm, or macroscopic invasive FTC	√
	√	Distant metastases	√
	√	Macroscopic tumor invasion	√
	√	Incomplete tumor resection
	√	Thyroglobulinemia out of proportion to what is seen on the post-therapy scan

*Aggressive histology includes tall cell, insular, columnar, diffuse sclerosing, trabecular solid, poorly differentiated variants of papillary thyroid carcinoma (PTC) and Hürthle cell variant of follicular thyroid carcinoma (FTC); MACIS: Metastases, Age, Completeness of resection, Invasiveness, Size of tumor; staging system developed at Mayo Clinic (16); TNM: Tumor, Nodes, Metastases, staging system developed by AJCC/UICC (21).