Skip lateral lymph node metastasis leaping over the central neck compartment in papillary thyroid carcinoma.

Objective: This study was performed to investigate the frequency and pattern as well as the predictive factors of skip metastasis (lateral cervical lymph node metastasis without central lymph node metastasis) in papillary thyroid carcinoma (PTC).

Methods: 450 PTC patients who received total thyroidectomy with central neck dissection(CND) combined with modified radical lateral neck dissection(LND) were divided into two groups: with or without skip metastases. The clinicopathological characteristics were statistically compared and analyzed, and univariate and multivariate analyses were performed to detect the risk factors of skip metastasis.

Results: The skip metastasis rate was 8.7% (39/450), and patients with skip metastases had fewer lateral lymph node metastases but were more likely to have single-level lateral metastasis, which are considered Level II(P<0.05). Skip metastasis was significantly associated with the primary tumor location in the upper portion (OR=18.495, 95% CI 6.612-51.731), a primary tumor size ≤10mm (OR=32.492, 95% CI 11.973-88.174) and Capsule invasion (OR=5.822, 95% CI 1.954-17.343) as demonstrated by our prospective study of 10 patients who received an injection of 0.1 ml carbon nanoparticles under ultrasonography in the upper portion of the lobe: 7(70%) had lateral compartment lymph node black staining without ipsilateral center compartment lymph node staining. However, skip metastasis did not affect the PTC patients' long-term tumor-free survival rate (P=0.432).

Conclusion: Skip metastases can be common, and the primary tumor location in the upper portion, a primary tumor size ≤10 mm, and capsular invasion are closely linked to skip metastasis. The lateral compartment should be carefully evaluated.