Validating the 'CUT score' risk stratification tool for indeterminate thyroid nodules using the Bethesda system for reporting thyroid cytopathology

Purpose: Managing intermediate thyroid nodules remains challenging. The CUT score is an Italian metanalysis-based cytologic (SIAPEC-IAP) scoring system, designed to assist clinicians. However, it was never evaluated against the Bethesda system for reporting thyroid cytopathology (BSRTC). This study aims to validate its utility for BSRTC III and IV nodules in a non-Italian population.

Methods: We collected all BSRTC III and IV thyroid nodules with a documented final pathology between 2010 and 2020. We calculated the C + U components of the CUT score using retrospective clinical (C) data collection and reevaluation of preoperative sonography (U) examination. The cytology (T) component which originally referred to the five-tiered SIAPEC-IAP cytologic classification was replaced by the corresponding BSRTC categories. Optimal test performances were calculated using receiver operating characteristic (ROC) curve analysis. Data were analyzed twice with considering of NIFTP as benign and as malignant.

Results: After exclusions, 62 nodules from 61 patients were included (50% BSRTC III, 50% BSRTC IV). Malignant nodules demonstrated a significantly higher C + U score compared with benign in both categories. The C + U cutoff value for BSRTC III was 5.25 (sensitivity and specificity of 69.23% and 66.67%, respectively, AUC = 0.72, p-value = 0.016), and 5.75 for BSRTC IV (sensitivity and specificity of 85.7% and 76.5%, respectively, AUC = 0.84, p-value < 0.001).

Conclusion: Our study suggests that the CUT score is applicable for both BSRTC III and IV nodules, and highlights the need for internal validations, since the cutoffs found were higher than previously reported.