This is a randomized study evaluating selective fine-needle aspiration cytology based on structured ultrasound using EU-TIRADS versus non-selective ultrasound guided cytology. Primary outcome is frequency of suspicious cytology (Bethesda III-VI) which is expected to be higher in the selective group compared to the non-selective group. Secondary outcome is the frequency of malignancy which is expected to be equal in both groups. However, the investigators do not expect to reach statistical significance for the secondary outcome according to power calculations.

Thyroid nodules are common in the population, and the reported incidence of thyroid cancer is increasing in most parts of the world. Palpable thyroid nodules are reported in 4-5 per cent of the population, of which 5-10 per cent are malignant. The reported incidence of thyroid nodules on ultrasound is higher.

EU-TIRADS has been shown in retrospective cohort studies to accurately stratify thyroid nodules with respect to risk of thyroid cancer. EU-TIRADS has been used in Western Sweden since 2017 and in 2021 it was implemented in the Swedish National Guidelines for thyroid cancer. To the knowledge of the investigators, no randomized controlled study has been carried out validating EU-TIRADS. This multicenter regional study aims to investigate the safety of using selective cytology using EU-TIRADS. Primary outcome is the result of cytology suspicious of thyroid cancer. In the selective group, low risk nodules will not undergo cytology and therefore the frequency of cytologically suspicious nodules (Bethesda III-VI) is expected to be higher in this group.

Inclusion Criteria:

• Patients referred to ultrasonography of the thyroid due to goiter symtoms or positive findings on FDG-PET

Exclusion Criteria:

• Patients previously examined with ultrasonography of the thyroid
• Patients who have previously undergone thyroid surgery

All IPD will be made available including data, study protocol, statistical analysis plan and informed consent form.

Data will be available from six months to ten years after last patient inclusion in the study.

Upon reasonable request data from the study will be made available by email to dr Jakob Dahlberg (jakob.dahlberg@vgregion.se) or dr Andreas Muth (andreas.muth@vgregion.se).