Preoperative Prediction of Lymph Node Metastasis in T1N0M0 Papillary Thyroid Carcinoma by Using Contrast-enhanced Ultrasound

Inclusion Criteria 1. Patients with preoperative assessment of T1N0M0 papillary thyroid carcinoma who underwent initial surgical treatment at the medical centers participating in this study between June 2018 and June 2025. 2. Definitive diagnosis of papillary thyroid carcinoma confirmed by postoperative histopathological examination. 3. Preoperative conventional ultrasound and contrast-enhanced ultrasound (CEUS) examination of the thyroid and/or suspicious central lymph nodes were performed, with complete imaging data of acceptable quality for analysis. 4. Surgical procedures included thyroidectomy (lobectomy or total thyroidectomy) combined with central lymph node dissection (prophylactic or therapeutic) to provide a definitive pathological gold standard for lymph nodes. 5. Complete clinical pathological data and imaging data were retrievable from the Hospital Information System (HIS). Exclusion Criteria 1. Preoperative receipt of any anti-tumor treatment targeting the thyroid (e.g., radiotherapy, chemotherapy, targeted therapy, or ablation therapy). 2. Complication with other types of thyroid malignant tumors (e.g., medullary carcinoma, undifferentiated carcinoma, etc.). 3. History of neck surgery or radiotherapy that may affect the structure of cervical lymph nodes. 4. Complication with other systemic diseases that may affect CEUS perfusion characteristics or imaging evaluation (e.g., severe heart failure, liver cirrhosis, etc.). 5. Allergy to components of the ultrasound contrast agent. 6. Missing key clinical or imaging data, making complete analysis impossible.