Value of preoperative ultrasound in evaluating of N stage of papillary thyroid carcinoma and predictive factors of lymph node metastasis

Objective To evaluate the value of preoperative ultrasound in evaluating N stage of human papillary thyroid carcinoma and its predictive factors of lymph nodes metastasis. Methods All 358 patients with papillary carcinoma confirmed by surgery and pathology were retrospectively analyzed. The American Joint Committee on Cancer (AJCC) thyroid cancer staging system (8th edition) was used as a standard, and postoperative pathological results were used as the golden criteria, 358 cases were divided into pN0 stage group (no lymph node metastasis), pN1a stage group (central lymph node metastasis), and pN1b stage group (lateral lymph node metastasis). The clinical predictive factors between different groups were compared (gender, age, tumor size, multifocal, extramural invasion, hashimoto thyroiditis, BRAF mutation), and the consistency of preoperative sonographic N stage and actual pathological N stage were analyzed. We try to find the capacity of the evaluation the N stage of papillary carcinoma by preoperative ultrasound examination, and the clinical predictive factors that may affect N stage. Results All 358 patients underwent cervical lymph node dissection. Results showed 196 patients in pN0 group, 129 patients in pN1a group, and 33 patients in pN1b group. The N stage evaluated by preoperative ultrasound was basically consistent with the actual pathological N stage (Kappa=0.320, P<0.01). Between the pN0 group and the pN1 group, the age, the tumor size and the BRAF mutuation was significantly different (χ2=10.214, 4.818 and 7.126, P<0.05 for all). Between the pN1b group and the non-pN1b group (pN0+ pN1 group), tumor size, multifocality of tumor, and extrathyroid extention (ETE) were significantly different between these groups (χ2=10.638, 14.193 and 9.330, P<0.01 for all). Conclusion Preoperative ultrasound is useful in evaluating the N stage of thyroid papillary carcinoma, which can provide clinical support for diagnosis and treatment. Patients 1 cm and BRAF mutation positive are more likely to develop to pN1 phase. In the pN1b stage, tumors >1 cm, multifocal cancer and capsular invasion are more common. Key words: Ultrasonography; Thyroid carcinoma; N staging