- Macroscopic invasion of tumor into the perithyroidal soft tissues - Incomplete tumor resection - Distant metastases - Postoperative serum thyroglobulin suggestive of distant metastases - Pathologic N1 with any metastatic lymph node ≥3 cm - Follicular thyroid cancer with extensive vascular invasion (>4 foci). Here, TG is linked to thyroid gland follicular carcinoma.