Integrating Clinical Parameters into Thyroid Nodule Malignancy Risk: A Retrospective Evaluation Based on ACR TI-RADS

Abstract

Background/Objectives: Thyroid nodules are commonly found through sensitive imaging methods like ultrasonography. While most nodules are benign and asymptomatic, certain characteristics may indicate malignancy, prompting fine needle aspiration biopsy. Factors like age and gender affect cancer risk, complicating ultrasound-based risk systems. We aimed to determine whether the cytological malignancy rate of thyroid nodules could be adjusted for several clinical parameters. Methods: Data from patients aged 18 and above with thyroid nodules assessed via fine needle aspiration (FNA) were retrospectively reviewed. Malignancy classification was based on cytopathology and histopathology results. The study examined how various clinical parameters, adjusted for the ACR TI-RADS category, affected thyroid nodule malignancy rates, including age, sex, Body Mass Index (BMI), nodule size, presence of autoimmunity, and thyroxine therapy. Additionally, we analyzed the performance of ACR TI-RADS in predicting malignant cytology across different age subgroups of thyroid nodules. Results: The study included 1128 thyroid nodules from 1001 adult patients, with a median age of 48 years and predominantly female (76.68%). Malignancy rates varied across ACR TI-RADS categories, with higher rates associated with larger nodules and younger age groups. Age emerged as a significant predictor of malignancy, with a consistent decrease in the odds ratio for malignant cytology with advancing age across all ACR TI-RADS categories, indicating its potential utility in risk assessment alongside nodule size and sex. Conclusions: Raising the size threshold for recommending FNA of TR3-3 nodules and incorporating patients' age and gender into the evaluation process could enhance the system's accuracy in assessing thyroid nodules and guiding clinical management decisions.

Keywords: Thyroid Imaging Reporting and Data System; age; malignancy; thyroid nodules.

Figure 1

Stratification of the 705 thyroid nodules with an indication for FNA in ACR-TIRADS categories. ACR TI-RADS: American College of Radiology Thyroid Imaging Reporting and Data System. FNA: fine needle aspiration. Percentile refers to the total study population.

Figure 2

Receiver operating characteristic (ROC) curve illustrating the diagnostic performance of nodule size in predicting cytological malignancy among thyroid nodules classified as ACR TI-RADS category 3 (TR3). The analysis identified an optimal size cutoff of 34 mm, yielding a sensitivity of 83.3% and specificity of 73.1% (area under the curve (AUC) = 0.794). The curve is based on data from 182 nodules with an indication for fine needle aspiration (FNA). Prevalence of malignancy 15.2% (reported by the guidelines: <5%). Youden index 0.564. Abbreviations: ROC, receiver operating characteristic; AUC, area under the curve; TI-RADS, Thyroid Imaging Reporting and Data System; FNA, fine needle aspiration. Black dot = Youden Index.

Figure 3

Receiver operating characteristic (ROC) curve assessing the diagnostic value of patient age in predicting cytological malignancy among thyroid nodules classified as ACR TI-RADS category 5 (TR5). The optimal age cutoff, determined by the Youden index (0.215), was ≤43 years. This threshold yielded a sensitivity of 50.3% and specificity of 71.2% for malignancy detection (AUC and 95% CI not shown). Data are derived from a retrospective analysis of 278 nodules evaluated for fine needle aspiration (FNA). Abbreviations: ROC, receiver operating characteristic; TI-RADS, Thyroid Imaging Reporting and Data System; FNA, fine needle aspiration. Black dot = Youden Index.

Figure 4

Proposed framework for integrating clinical variables into ACR TI-RADS-based malignancy risk estimation.