Thyroid malignancy rate in various subtypes of thyroid nodules

Merah Al Busaidy; Kevin Burke; Gina Dennehy; Diarmuid Smith; Mark Sherlock; Michael W O; Krzysztof Wanic; Paul O; Arnold Hill; Martina Morrin; Ruth Dunne; John Cunningham; Cliona Ryan; Amar Agha

doi:10.1530/endoabs.115.EP2

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Endocrine Abstracts (2026) 115 EP2 | DOI: 10.1530/endoabs.115.EP2

IES2025 Research, Audit and Quality Improvement Projects E-Posters (60 abstracts)

Thyroid malignancy rate in various subtypes of thyroid nodules

Merah Al Busaidy ¹ , Kevin Burke ¹ , Gina Dennehy ¹ , Diarmuid Smith ¹ , Mark Sherlock ¹ , Michael W O’Reilly ¹ , Krzysztof Wanic ¹ , Paul O’Neill ² , Arnold Hill ² , Martina Morrin ³ , Ruth Dunne ³ , John Cunningham ³ , Cliona Ryan ⁴ & Amar Agha ¹

Author affiliations

¹Department of Endocrinology, Beaumont Hospital, Dublin, Ireland; ²Department of Surgery, Beaumont Hospital, Dublin, Ireland; ³Department of Radiology, Beaumont Hospital, Dublin, Ireland; ⁴ Department of Histopathology, Beaumont Hospital, Dublin, Ireland

Introduction: Thyroid nodules are common, with a prevalence of around 50% in the general population. Ultrasound characterisation using the British Thyroid Association (BTA) U classification system is widely used in the UK and Ireland. Limited data exist on malignancy rates in thyroid nodules, particularly those with an indeterminate appearance (U3). Moreover, significant interobserver variability in reporting classification highlights the need for locally generated data.

Methodology: We assessed malignancy rates among U-classified thyroid nodules that underwent fine needle aspiration cytology (FNAc), reported using the Royal College of Pathologists Thy classification (Thy1-Thy5)

Results: Of 200 nodules assessed (median size 2.8 cm, range 0.8–10.6 cm), 84% were U 3 (indeterminate malignancy risk); 17 of these (8.5%) were malignant. Papillary thyroid carcinoma was the most common malignancy. Two nodules were metastatic from non-thyroidal primaries. Among 19 Thy 1 (inadequate sample) nodules, one was subsequently confirmed malignant. Of 139 Thy 2 (benign) nodules, three (1.5%) were malignant on repeat FNAc. All Thy 5 nodules were confirmed malignant. Among 17 U 4 nodules, four (24%) were diagnosed as malignant. Overall, 24 of 200 nodules (12%) were malignant.

Conclusion: Malignancy rates in thyroid nodules, including 8.5% in indeterminate U 3 cases, are consistent with those reported in other specialised centres and classification systems.