Endocrine Abstracts

Introduction: Most thyroid nodules are benign. Some studies have shown largest nodule size, specially >4 cm, can predict malignancy and reduce fine needle aspiration (FNA) accuracy. Recent studies, however, have shown conflicting results as to whether nodule size may be used to distinguish at risk-lesions. We attempt to determine whether nodule size predicts thyroid malignancy and to examine accuracy of fine needle aspiration (FNA) by size.

Material and methods: A multicenter, retrospective analytical study was performed on a total of 882 patients with thyroid solitary nodules and put underwent partial or total thyroidectomy between 2010 and 2013. We compared nodules by size cutoffs using Chi-squared and Fisher exact test where appropriate. Binary logistic regression analysis was used to identify the independent factors associated with thyroid malignancy. All data were analyzed using SPSS software for Windows (version 18.0).

Results: Of the 882 nodules, 664 (73%) were benign and 238 (27%) malignant. Nodules <2 cm had the highest malignancy rate (49.2%). Decreasing malignancy rates (23.1, 16.8, 4.6, and 6.3%) were observed with increasing size (2–3 cm, 3–4 cm, 4–5 cm, >5 cm). Thyroid nodule size > 4 cm was associated to less risk of malignancy (OR O.589 (0.421–0.824)). After adjusting for patient age and gender, nodules that measured >4 cm had a greater malignancy risk compared to those measuring <4 cm (OR 2.031 (P:0.001)). In nodules with a benign FNA diagnosis (Bethesda II), the overall malignancy rate (false negative rate) was 10% (35/349). The highest false negative rates (15%) were in nodules <2 cm. There was no significant difference in the false negative rates for nodules >4 cm (8%) or <4 cm (10%) respectively.

Conclusions: After adjusting for patient age and gender, nodules that measured >4 cm had a greater malignancy risk. The false negative rates were not higher for nodules >4 cm. Thyroidectomy should not be recommended based solely on nodule size.