*2.3. Cytopathology and Histopathology*

Aspiration was performed by two pathologists (FP and CDB) with 10 years of experience in thyroid FNA under US guidance with 22–25 gauge diameter needles. The aspirated material was smeared onto 3–4 traditional slides per nodule. The slides were fixed with spray alcohol (Cytofix, propan-2-ol) and then stained with Papanicolau, or air-dried and

stained with May–Grunwald Giemsa. Cases were diagnosed according to two standard systems for reporting thyroid cytopathology: the Italian Society of Pathology classification (SIAPEC) and the Bethesda System [12,13]. The TIRADS indication of FNA was considered correct in the presence of a cytology ≥TIR3A/III (SIAPEC/Bethesda). TIR1c-TIR2 patients and those with TIR3 who did not undergo surgery, underwent a US examination 12 months after the first US-guided FNA performed by the same radiologist [14]. Nodules were considered benign in the absence of the following conditions:


A histological evaluation was performed on the surgical specimens of total or hemithyroidectomy [15]. The tissue was formalin-fixed, paraffin-embedded, and stained with haematoxylin and eosin. The ROM was estimated according to histological evaluation or US follow-up examination.
