EU-TIRADS classification of thyroid nodules — Frequently asked questions (FAQ)
1) What is the EU-TIRADS system?
The EU-TIRADS (European Thyroid Imaging Reporting and Data System) is an ultrasound risk-stratification system developed by the European Thyroid Association to estimate the risk of malignancy in thyroid nodules. It helps standardise ultrasound reports and guide decisions regarding the need for fine-needle aspiration cytology (FNAC).
2) What are the EU-TIRADS categories?
The system classifies nodules into four main categories: EU-TIRADS 2 (benign), EU-TIRADS 3 (low risk), EU-TIRADS 4 (intermediate risk) and EU-TIRADS 5 (high risk). The risk of malignancy increases progressively according to the ultrasound features identified.
3) What are the highly suspicious ultrasound features?
The main highly suspicious features include marked hypoechogenicity, microcalcifications, irregular margins, a non-oval shape (taller than wide) and suspicious cervical lymph nodes. The presence of any of these findings significantly increases the likelihood of malignancy.
4) When is fine-needle aspiration cytology indicated?
The indication for FNAC depends on the combination of the EU-TIRADS category and the size of the nodule. In general, FNAC is recommended for EU-TIRADS 5 nodules ≥10 mm, EU-TIRADS 4 nodules ≥15 mm and EU-TIRADS 3 nodules ≥20 mm. Benign nodules classified as EU-TIRADS 2 rarely require cytology.
5) Should a small but highly suspicious nodule be biopsied?
Not always. In EU-TIRADS 5 nodules smaller than 10 mm, active surveillance may be appropriate, although FNAC can be considered in selected situations, such as young age, documented growth, suspicious lymph nodes or a high level of clinical concern.
6) What does an EU-TIRADS 2 nodule mean?
Nodules classified as EU-TIRADS 2 usually correspond to simple cysts or spongiform nodules and have a very low or virtually absent risk of malignancy. They generally do not require FNAC, except in specific situations.
7) Does the EU-TIRADS system apply to all nodules?
The system was developed for nodules assessed by ultrasound, but interpretation should be integrated with clinical and laboratory findings. In patients with a low TSH, thyroid scintigraphy may be required before deciding whether FNAC should be performed.
8) Do hyperfunctioning nodules require FNAC?
As a general rule, hyperfunctioning (“hot”) nodules have a very low risk of malignancy. In these cases, the priority is functional assessment and treatment of any associated hyperthyroidism, and FNAC is rarely required.
9) What should be done after a benign cytology result?
Following a benign cytology result (Bethesda II), periodic clinical and ultrasound surveillance is recommended. Repeat FNAC should be considered if there is significant nodule growth or the development of new suspicious ultrasound features.
10) Does nodule growth necessarily mean cancer?
No. Many benign nodules may increase in size over time. However, a significant increase in volume or the development of new suspicious ultrasound features warrants reassessment and possible repeat cytology.
11) When should FNAC be repeated?
Repeat FNAC should be considered when there is relevant nodule growth, the development of new suspicious ultrasound features or when the initial cytology was non-diagnostic. The decision should be individualised according to the clinical and imaging risk.
