*2.1. Patients Selection*

This prospective study included 448 consecutive patients who underwent 493 USguided FNA from January to June 2019 at the interventional radiology clinic, ASST Monza, Italy, during an Italian Association for Research on Cancer (AIRC)-granted project for the diagnosis of thyroid carcinoma [8]. All nodules were subjected to FNA, regardless of their ACR/EU-TIRADS scores, after an endocrinological clinical indication. Thirteen lesions with an unsatisfactory cytology and no FNA repetition were excluded for a final set of 480 nodules and 435 subjects. Histology was available in 49 resected nodules. US was performed at the 12-month follow-up visit in 352 patients, while 79 cases, corresponding to 70 TIR3A/III, 8 TIR3B/IV, and 1 TIR4/V, were lost to follow-up. This study was approved by the ASST Monza Ethical Board (October 2016, 27102016) and appropriate informed consent was obtained from all patients.
