Table 2.

Risk stratification according to the ATA and ETA guidelines

ATA risk stratification low risk	Intermediate risk	High risk
No local or distant metastases All macroscopic tumor has been resected No tumor invasion of locoregional tissues or structures No aggressive histology or vascular invasion If 131I was given, no 131I uptake outside the thyroid bed on the post-therapeutic WBS	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-therapeutic WBS or Tumor with aggressive histology or vascular invasion	Macroscopic tumor invasion Incomplete tumor resection Distant metastases Thyroglobulinemia out of proportion to what is seen on the post-ablative scan

ETA risk stratification very low risk	Low risk	High risk
Complete surgery Patients with unifocal microcarcinoma (<1 cm) with no extension beyond the thyroid capsule and without lymph node metastases	No local or distant metastases No tumor invasion of locoregional tissues or structures No aggressive histology or vascular invasion	Less than total thyroidectomy Tumor invasion of locoregional tissues or structures Cervical lymph node metastases Distant metastases Aggressive histology or vascular invasion