Decoding Lymph Node Skip Metastasis: Impact on Long-Term Outcomes in Stage T1 Papillary Thyroid Carcinoma

Abstract Background Skip metastasis of lateral cervical lymph nodes not uncommonly occurs in early papillary thyroid carcinoma (PTC), which represents a heterogeneous metastasis type. Currently, few studies report on the relationship between skip metastasis and prognosis or propose treatment recommendations. Methods A retrospective analysis was conducted on patients with unilateral T1-stage PTC who underwent lobectomy between 2007 and 2015. Patients with skipping N1b (sN1b) stage were included, and propensity score matching (PSM) was applied to incorporate patients from both N1a and N1b stages for comparison. Kaplan-Meier method was employed to compare recurrence-free survival (RFS) among different groups, and lymph node metastasis patterns in sN1b group as well as their impacts on prognosis were evaluated. Results The initial cohort comprised 1,188 patients, and after adjusting for baseline clinicopathological data and follow-up duration, a total of 372 patients were included with an average follow-up time of 82 months. The recurrence rates in the N1a, sN1b, and N1b groups after PSM were 8.9%, 11.3%, and 12.9%, respectively. Notably, RFS did not differ significantly between sN1b and N1a(P=0.65) or N1b(P=0.66). Furthermore, the number of positive lymph nodes in the sN1b group was comparable to N1a group (P=0.77) but significantly lower than N1b group (P<0.0001). Remarkably, the risk stratification based on the lymph node positivity rate (LNPR) in the sN1b group demonstrated a strong prognostic discrimination (P=0.0067). Conclusion The RFS among stage T1 PTC patients with sN1b stage was comparable to those with N1a and N1b stages. LNPR risk stratification emerged as a significant prognostic factor.