Assessing Predictive Utility of Ultrasound for Tumor Characteristics in Thyroid Cancer

OBJECTIVE: To evaluate the accuracy of preoperative ultrasound in estimating tumor size, multifocality, and extrathyroidal extension in papillary thyroid carcinoma. METHODS: A retrospective cohort study was conducted at a tertiary referral center, including patients who underwent curative surgery for papillary thyroid carcinoma between 2006 and 2022. Agreement between preoperative ultrasound-estimated and postoperative pathologic tumor size was assessed overall and across predefined size categories (≤ 1 cm, 1-2 cm, 2-3 cm, 3-4 cm, and > 4 cm). The diagnostic performance of ultrasound for detecting multifocality and extrathyroidal extension was also evaluated. RESULTS: The medical records of a total of 931 patients were reviewed. The mean sonographic and pathologic tumor sizes were 2.10 ± 1.42 cm and 1.64 ± 1.28 cm, respectively (p < 0.001). Ultrasound consistently overestimated tumor size across all groups, with the mean percentage difference rising from 6% in tumors ≤ 1 cm to 32% in tumors > 4 cm (p < 0.001). The overall mean percent difference was +15.7 ± 40.7%, indicating bias toward larger sonographic measurements. Ultrasound detection of extrathyroidal extension showed a positive predictive value of 30% and a negative predictive value of 95%; a positive predictive value of 40% and a negative predictive value of 85% for multifocality. CONCLUSION: Our findings indicate that ultrasound tends to overestimate tumor size and that it has limited predictive accuracy for multifocality and extrathyroidal extension. They demonstrate the need for caution when planning a total thyroidectomy based solely upon preoperative ultrasound findings in the absence of suspected nodal metastasis.