| Low risk | *Papillary thyroid cancer (with all of the following) No local or distant metastases *All macroscopic tumors 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 131I 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 5 pathologic N1 micro metastases (< 0.2 cm in largest dimension) Intrathyroidal, encapsulated follicular variant of papillary thyroid cancer *Intrathyroidal, well differentiated follicular thyroid cancer with capsular invasion and no or minimal (< 4 foci) vascular invasion Intrathyroidal, papillary microcarcinoma, unifocal or multifocal, including BRAF-V600E mutated (if known) |
| Intermediate risk | *Microscopic invasion of tumor into the perithyroidal soft tissues *RAI-avid metastatic foci in the neck on the first post-treatment whole-body RAI scan Aggressive histology (e.g., tall cell, hobnail variant, columnar cell carcinoma) Papillary thyroid cancer with vascular invasion *Clinical N1 or > 5 pathologic N1 with all involved lymph nodes < 3 cm in largest dimension Multifocal papillary microcarcinoma with ETE and BRAFV600E mutated (if known) |
| High risk | *Macroscopic invasion of tumor into the perithyroidal soft tissues (gross ETE), Incomplete tumor resection *Distant metastases *Postoperative serum thyroglobulin suggestive of distant metas-tases Pathologic N1 with any metastatic lymph node 3 cm in largest dimension |