Risk factors for skip metastasis and lateral lymph node metastasis of papillary thyroid cancer.

BACKGROUND: Lymph node metastases from papillary thyroid cancer is believed to disseminate sequentially, first to the central neck and later to the lateral neck. Skip metastases of papillary thyroid cancer, however, are defined as lateral lymph node metastasis without central lymph node metastasis. The aim of this study was to investigate the risk factors for skip metastases and lateral lymph node metastasis of papillary thyroid cancer.

METHODS: We reviewed 721 papillary thyroid cancer patients undergoing total thyroidectomy with central lymph node dissection and lateral lymph node dissection during 2013 to 2018. Multivariate logistic regression analysis was performed to identify clinicopathologic risk factors for skip metastasis and lateral lymph node metastasis of papillary thyroid cancer.

RESULTS: The rate of skip metastases was 7.4% (42 of 567 patients). Multivariate analysis showed that female sex and papillary thyroid microcarcinoma (≤ 1 cm) were independent risk factors for skip metastases, with odds ratios ([OR], 95% confidence interval [CI]) of 2.29 (1.02-5.16) and 2.84 (1.46-5.16), respectively. Intrathyroidal spread of papillary thyroid cancer and an increased number of central lymph nodes dissected were inversely associated with skip metastases with ORs (95% CI) of 0.13 (0.02-0.99) and 0.88 (0.83-0.94), respectively. In contrast, a greater tumor size, central lymph node metastasis, an increased number of central lymph nodes dissected, and an increased number of lateral lymph nodes dissected were associated with a lateral lymph node metastasis risk of papillary thyroid cancer, with ORs (95% CI) as follow: 1.67 (1.08-2.59), 3.07 (1.71-5.52), 1.25 (1.14-1.37), and 1.07 (1.04-1.10), respectively, by multivariate analysis.

CONCLUSION: Greater tumor size, central lymph node metastasis, and an increased number of both central lymph nodes and lateral lymph nodes dissected were predictors for lateral lymph node metastasis of papillary thyroid cancer. In addition, papillary thyroid microcarcinoma was an independent risk factor for skip metastases. A complete and comprehensive central compartment dissection may decrease the false-positive detection of skip metastases of papillary thyroid cancer.