Table 2.

Defining Low Risk Based on Recurrence

ATA Risk Stratification
PTC (with all of the following):
	No local or distant metastases
	All macroscopic tumor has been resected
	No tumor invasion of loco-regional tissues or structures
	The tumor does not have aggressive histology (e.g., tall cell, hobnail variant, columnar cell carcinoma)
	If I-131 is given, there are no RAI-avid metastatic foci outside the thyroid bed on the first post-treatment whole-body RAI scan
	No vascular invasion
	Clinical N0 or ≤five pathologic N1 micrometastases (<0.2 cm in largest dimension)
Intrathyroidal, encapsulated follicular variant of PTC
Intrathyroidal, well-differentiated follicular thyroid cancer with capsular invasion and no or minimal (<four foci) vascular invasion
Intrathyroidal, papillary microcarcinoma, unifocal, or multifocal, including BRAF V600E mutated (if known)

Data from Haugen et al. (8).

Abbreviations: I-131, iodine-131; N0, no evidence of regional lymph node metastasis; N1, metastases to cervical/upper mediastinal lymph nodes.