Indications for FNA of Thyroid Nodules: EU-TIRADS and Bethesda System
Risk Stratification: EU-TIRADS
For assessing the risk of malignancy in thyroid nodules in adults, the European Thyroid Association proposed the EU-TIRADS system (Russ G, Bonnema SJ, Erdogan MF et al., European Thyroid Association Guidelines for Ultrasound Malignancy Risk Stratification of Thyroid Nodules in Adults: The EU-TIRADS. Eur Thyroid J 2017). The system classifies nodules based on ultrasound features and serves as a basis for deciding on FNA. Specific ultrasound criteria for categories and size thresholds for biopsy indication are not detailed in the provided excerpts [clarify].
Role of Multiparametric Ultrasound (MPUS)
According to the EFSUMB Guidelines on Multiparametric Ultrasound Thyroid Nodule Evaluation (Cantisani et al., 2026), MPUS is applied in several typical clinical situations: cytologically indeterminate nodules, multinodular goiter, assessment of extrathyroidal extension of malignant nodules. Additionally, MPUS is considered as support during thyroid biopsy/aspiration and in staging cervical lymph nodes.
Interpretation of Cytology: Bethesda System
FNA results are interpreted according to The 2017 Bethesda System for Reporting Thyroid Cytopathology (Cibas ES, Ali SZ, Thyroid 2017). This system standardizes cytological reports and determines further management. Specific Bethesda categories and associated malignancy risks are not provided in the given excerpts [clarify].
It is noted that the proportion of nondiagnostic cytological results may change when using TIRADS before and after the Bethesda system is applied (Yoon JH et al., Radiology 2015).
Final Algorithm
Ultrasound assessment according to EU-TIRADS determines the indication for FNA; the obtained material is classified according to the Bethesda system. For cytologically indeterminate nodules, MPUS may additionally be employed. Exact size thresholds and criteria for each system require clarification from the full texts of the respective guidelines [clarify].
Frequently asked questions
Which system is used for ultrasound risk stratification before FNA?
EU-TIRADS by the European Thyroid Association (Russ G et al., Eur Thyroid J 2017).
Which system is used to interpret FNA results?
The 2017 Bethesda System for Reporting Thyroid Cytopathology (Cibas ES, Ali SZ, Thyroid 2017).
When is multiparametric ultrasound (MPUS) applied?
In cases of cytologically indeterminate nodules, multinodular goiter, assessment of extrathyroidal extension, as support for biopsy/aspiration, and in staging cervical lymph nodes (EFSUMB, Cantisani et al., 2026).
Are specific size thresholds for FNA provided in the excerpts?
No, specific size thresholds for each EU-TIRADS category are not provided in the given excerpts [clarify].
Does Bethesda affect the proportion of nondiagnostic results?
The proportion of nondiagnostic cytological results may change when using the Bethesda system in combination with TIRADS (Yoon JH et al., Radiology 2015).