Predictive Value of Tumor Size for Thyroid Nodule Malignancy

Objectives: This study assessed the association between tumor size and malignancy risk in thyroid nodules, and evaluated the diagnostic performance of fine-needle aspiration (FNA) compared to histopathology. It also examined the influence of demographic factors such as age, sex, and body mass index (BMI) on malignancy risk. Methods: A retrospective cross-sectional analysis was conducted on 722 patients who underwent total thyroidectomy at a tertiary hospital in Riyadh, Saudi Arabia, between January 2010 and December 2023. Tumor size, FNA results, histopathology, and demographic variables were collected. Statistical analyses included correlation testing, regression modeling, and diagnostic accuracy metrics. Results: Tumor size had a moderate correlation with malignancy based on FNA (r = 0.42) and a very strong correlation with histopathology (r = 0.96). FNA showed a sensitivity of 72.8% and specificity of 70.5%, with reduced accuracy in larger tumors. Higher malignancy rates were observed in patients aged ≥45 years and those with elevated BMI. Conclusion: Tumor size is a strong predictor of malignancy in thyroid nodules, particularly when assessed by histopathology. FNA shows reduced sensitivity in larger nodules, highlighting the need for multimodal evaluation strategies. Demographic risk factors further influence diagnostic outcomes. These findings emphasize the need for region-specific diagnostic guidelines that consider both tumor characteristics and patient profiles.