Background: After diagnosing well-differentiated thyroid cancer (WDTC), assessment of the risk for disease-specific recurrence is essential for deciding between hemi-thyroidectomy (HT) and total thyroidectomy (TT). The American Thyroid Association (ATA) 2015 guidelines suggest that patients with 1-4 cm WDTC without suspicious features may be suitable for HT. Patients' preoperatively determined risk levels are re-stratified according to surgical and final histopathological findings. The incidence and clinical implications of high-risk features discovered postoperatively in patients with preoperatively determined lowrisk WDTC are yet to be better defined.