Clinical impact of the new SIAPEC-IAP classification on the indeterminate category of thyroid nodules

BACKGROUND: The increasing frequency in the diagnosis of thyroid nodules has raised a growing interest in the search for new diagnostic tools to better select patients deserving surgery. In 2014, the major Italian Societies involved in the field drafted a new cytological classification, to better stratify pre-surgical risk of thyroid cancer, especially for the indeterminate category, split into TIR3A and TIR3B subclasses, associated to different therapeutic decisions. MATERIALS AND METHODS: This retrospective cross-sectional survey analyzed thyroid fine-needle aspiration biopsy performed at our outpatient clinic before and after the introduction of the new SIAPEC-IAP consensus in May 2014. RESULTS: 8956 thyroid nodules were included in the analysis: 5692 were evaluated according to the old classification and 3264 according to the new one. The new criteria caused the overall prevalence of TIR3 to increase from 6.1 to 20.1%. Of those, 10.7 and 9.4% were included in the TIR3A and TIR3B subgroups, respectively. Each of the 213 TIR3B nodules underwent surgery and 86 (40.4%) were diagnosed as thyroid cancer, while among the 349 TIR3A nodules, only 15 of the 60 that underwent surgery were found to be thyroid cancer. CONCLUSIONS: This analysis shows that the new SIAPEC-IAC criteria significantly increased the proportion of the overall TIR3 diagnosis. The division of TIR3 nodules into two subgroups (A and B) allowed a better evaluation of the oncologic risk and a better selection of patients to be referred to surgery.