Risk factors for high-volume lymph node metastases in cN0 papillary thyroid microcarcinoma

Background: Lymph node metastasis (LNM) often occurs in clinical lymph node negative (cNO) papillary thyroid microcarcinoma (PTMC). The risk factors for LNM, especially for high-volume LNM, were investigated in this study. Methods: The medical records of 1,974 consecutive PTMC patients admitted to the Peking Union Medical College Hospital (PUMCH) from 2013 to 2015 were reviewed. Their clinicopathological features were collected. Univariate and multivariate analyses were performed to identify the risk factors for LNM/high-volume LNM. Results: Of all the patients, cervical lymph node metastases were detected in 690 patients (34.95%), and high-volume LNM was detected in 75 patients (3.80%). The results of univariate analysis revealed that sex, age, chronic thyroiditis, multifocality, and tumor diameter were significantly correlated with LNM (P<0.05) and that sex, age, multifocality, and tumor diameter were significantly correlated with high-volume LNM (P<0.05). Multivariate logistic regression analysis demonstrated that male sex [odds ratio (OR) =1.657, P<0.001], multifocality (OR =1.601, P<0.001), and tumor diameter >0.5 cm (OR =1.770, P<0.001) were independent risk factors for LNM; age of 40-59 years old (OR =0.427, P<0.001), age >= 60 years old (OR =0.291, P<0.001), and chronic thyroiditis (OR =0.562, P<0.001) were independent protective factors for LNM. For high-volume LNM, male sex (OR =2.250, P=0.002), tumor diameter >0.5 cm (OR =3.664, P=0.013) and multifocality (OR =2.034, P=0.004) were independent risk factors, whereas age >= 40 years old (OR =0.240, P<0.001) was an independent protective factor. Conclusions: Lymph node metastases are common in cNO PTMC, whereas high-volume LNM is rare. Active surveillance may be reasonable for patients with tumor diameter <= 0.5 cm, age >= 40 years old, female sex and isolated lesions.