Predictive Value of Conventional Ultrasonographic Features Combined with Clinical Factors for Capsular Invasion in Papillary Thyroid Carcinoma with Hashimoto's Thyroiditis.

This retrospective study aimed to investigate the predictive value of conventional ultrasonographic features combined with clinical factors for capsular invasion in patients with papillary thyroid carcinoma (PTC) with concurrent Hashimoto's thyroiditis (HT). A total of 262 patients with pathologically confirmed PTC and concurrent HT who underwent surgery at our institution from January 2018 to June 2024 were included as the training cohort. Patients were divided into capsular invasion and non-capsular invasion groups according to postoperative pathological findings. Clinical characteristics, conventional ultrasonographic features, and preoperative serum thyroid-stimulating hormone (TSH) levels were compared between the two groups. Univariate and multivariate logistic regression analyses were performed to identify independent predictors of capsular invasion, and a nomogram model was constructed based on the selected variables. The predictive performance of the model was evaluated using receiver operating characteristic curves, calibration curves, decision curve analysis, and clinical impact curves. Univariate analysis showed that age, tumor diameter, postoperative lymph node metastasis, lesion margin, and blood flow signal were significantly associated with capsular invasion. Multivariate logistic regression analysis further identified age ≥55 years, larger tumor diameter, ill-defined lesion margin, and abundant blood flow signal as independent predictors of capsular invasion. The combined nomogram model achieved an area under the curve of 0.706 in the training cohort and 0.804 in the external validation cohort, showing better predictive performance than any single factor alone. Calibration curves, decision curve analysis, and clinical impact curves suggested acceptable model calibration and potential clinical utility. These findings indicate that a nomogram incorporating age, tumor diameter, lesion margin, and blood flow signal may provide a practical preoperative tool for estimating the risk of capsular invasion in patients with PTC and HT.