Beschreibung:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Objective</jats:title><jats:p>The Italian reporting system for thyroid cytology classifies indeterminate lesions as <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A (low risk) or <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B (high risk) and is meant to provide practical guidance rather than a detailed consideration of morphological features. We aimed to assess which cytological features have the most diagnostic value and whether they are effective in classifying nodules as either <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A or <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B and in predicting histological outcomes.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Thyroid fine‐needle aspirates from 111 indeterminate nodules were reviewed blinded to clinical information, <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A/<jats:styled-content style="fixed-case">TIR</jats:styled-content>3B classification, and histology in order to assess which cytological features (pooled into artefacts, smear background, architectural and nuclear atypia, and oncocytes) differentiate <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A from <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B, and benign from malignant histological outcomes.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Of the cytological features examined, those specific for <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B included high cellularity, nuclear atypia, oncocyte predominance and transgressing vessels. Features specific for <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A included artefacts, low cellularity and oncocyte sparseness. Other features, such as microfollicules/trabeculae, were non‐specific. Due to the different distributions of these features, three <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B subgroups were identifiable: follicular lesions with oncocytic changes, pure follicular lesions, and follicular lesions with nuclear atypia, whereas no subgroups were identifiable in <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A. Nuclear atypia was a significant indicator of malignancy, whereas oncocyte predominance was not a reliable predictor of malignancy. High cellularity and microfollicules/trabeculae were not indicative of any histological outcome.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>The majority of the assessed features were good predictors of histological outcomes. The <jats:styled-content style="fixed-case">TIR</jats:styled-content>3A category included undefined nodules due to the absence of characterising features, whereas the <jats:styled-content style="fixed-case">TIR</jats:styled-content>3B category included nodules with a greater number of distinguishing features.</jats:p></jats:sec>