The present study was conducted in accordance with the Declaration of Helsinki and approved by Ethics Committee of Nara Medical University (Approval no. 3048). Written informed consent was obtained from all patients involved. Between January, 2009 to December, 2018, 274 patients with PTC underwent lobectomy or total thyroidectomy at Nara Medical University (Kashihara, Japan) with or without paratracheal or lateral cervical lymph node dissection as an initial treatment. Patients were excluded if they were lost to follow-up for >3 years, had a history of distant metastasis at the time of the initial diagnosis, and had not undergone complete resection.