The impact of thyroid nodule size on the risk of malignancy in follicular neoplasms

Abstract

Background/aim: Studies have shown that the risk of malignancy in follicular neoplasms is as high as 30%. Often, surgery is recommended for such lesions, not for therapeutic purposes but as a diagnostic method, leading to increased hospital costs and related morbidities. Recent studies have suggested that tumor size predicts malignant potential of these follicular neoplasms. Our aim was to identify the impact of nodule size on the risk of malignancy for such lesions.

Patients and methods: A retrospective medical chart review was undertaken for patients who underwent thyroid surgery at a single academic North American Institution. A total of 120 follicular lesions, follicular neoplasms (Bethesda category IV) or follicular lesions of undetermined significance (Bethesda category III) in 110 patients undergoing thyroid surgery were evaluated. Nodule size as measured by ultrasound, fine-needle aspiration cytological results, and final histopathology reports were reviewed. Analysis was performed by classification according to nodule size: <3 cm, ≥3 cm, <4 cm and ≥4 cm.

Results: Out of the 120 nodules, 48 (40%) were reported to be malignant on final pathological examination. The malignancy rate in nodules<3 cm and ≥ 3cm was 41% and 37.8%, respectively (p=0.84). When 4 cm was used as the cut-off, the rate in nodules<4 cm and ≥4 cm was 40.6% and 37.5%, respectively (p=0.82).

Conclusion: Increased thyroid nodule size does not increase the malignancy rate for follicular neoplasms. Hence, we recommend against routine total thyroidectomy for patients with follicular neoplasms based on the size criteria.

Keywords: Nodule size; follicular lesion of undetermined significance; follicular neoplasms; thyroid cancer; thyroid malignancy.