Management and outcomes of small U3-U4 thyroid nodules: do sub-centimetre U3 nodules require biopsy?

OBJECTIVE: To evaluate management and outcomes of small (≤20 mm) U3-U4 thyroid nodules in UK practice and assess whether selected sub-centimetre U3 nodules require biopsy. METHODS: Retrospective cohort study at a UK district general hospital, including U3-U4 thyroid nodules ≤20 mm identified in 2022, with a follow-up to June 2025. The primary outcome was histologically confirmed thyroid malignancy. Secondary outcomes included fine-needle aspiration, cytology and surgical intervention. RESULTS: Eight-one nodules (73 patients) were included. Sixty-one nodules (75.3 per cent) underwent fine-needle aspiration and 31 nodules (38.3 per cent) underwent surgical procedure. The investigation was driven by ultrasound grade rather than size. Sub-centimetre nodules were less likely to be resolved by fine-needle aspiration or surgical procedure. Among the resected nodules, 26 out of 31 (83.9 per cent) were malignant, with no difference across size bands. CONCLUSION: Management of small U3-U4 nodules is determined by ultrasound grade and cytology rather than size. These findings support the consideration of a surveillance-first approach for selected sub-centimetre U3 nodules, provided the appropriate follow-up pathways are in place.