A nomogram for predicting lateral lymph node metastasis in cN0 unifocal papillary thyroid microcarcinoma

Abstract

Background Identifying risk factors for occult lateral LNM in PTMC can assist in determining the necessity of LND and other measures to reduce the risk of recurrence. This study aimed to establish a nomogram for predicting the probability of lateral lymph node metastasis (LLNM) in patients with cN0 unifocal papillary thyroid microcarcinoma (PTMC).Methods We retrospectively analyzed a total of 4872 patients with cN0 unifocal PTMC who were treated at our center from January 2013 to June 2018. Logistic regression tests were used to determine the risk factors for LLNM. A nomogram was constructed based on these risk factors.Results The rate of LLNM was 3.2%. Tumors located in the upper lobe (OR = 2.56, 95% CI 1.80–3.62; p < 0.001) and size greater than 7 mm (OR = 2.59, 95% CI 1.85–3.62; p < 0.001) had a 2.5-fold higher risk of LLNM than tumors in the lower or middle lobe and size less than or equal to 7 mm. Tumors with extrathyroidal extension (ETE) had a significantly higher risk of LLNM (OR = 1.41, 95% CI 1.01–1.99; p = 0.044). Having three or more central lymph node metastases (CLNMs) (OR = 5.84, 95% CI 3.83–8.93; p < 0.001) or having one or two CLNMs (OR = 2.91, 95% CI 1.93–4.42; p < 0.001) both had a higher risk of LLNM than having no CLNMs. A nomogram was developed based on these risk factors. The ROC curve for predicting LLNM showed that the AUC was 0.777, indicating a high degree of consistency.Conclusion Tumors located in the upper lobe, greater than 7 mm in size, ETE, and CLNMs, especially three or more, were independent risk factors for LLNM in cN0 unifocal PTMC. The nomogram based on these factors had favorable predictive value and consistency, but further prospective research is needed to validate these findings.