How Many Lymph Nodes are Enough in Thyroidectomy? A Cohort Study Based on Real-World Data

Thyroidectomy with only limited examination of lymph nodes is considered to pose potential risk for harboring occult nodal disease in patients with papillary thyroid cancer (PTC). However, the optimal number of examined lymph nodes (ELNs) in patients with PTC with clinically lateral lymph node metastasis (cN1b) remains unclear.

Patients with cN1b PTC who underwent therapeutic neck dissection were retrospectively enrolled. A β-binomial distribution was utilized to calculate the likelihood of occult nodal disease as a function of total number of ELNs, and recurrence-free survival analysis was performed using the Kaplan-Meier method.

Together 982 patients met the inclusion criteria for this study, of which 853 patients had node-positive disease. The median ELN count was 23 (interquartile range 14-33). Increased ELN counts were associated with a decreased rate of occult nodal disease. The prevalence of nodal metastasis was 84%, while the corrected prevalence was 90%. The estimated probability of false-negative nodal disease was 67% for patients with PTC when only a single node was examined. Survival analysis revealed that populations with higher probability of occult nodal diseases experienced significantly higher recurrence rate. For patient with cN1b PTC, 20 ELNs were required to achieve 95% confidence of having no occult nodal disease. Minimum thresholds of 24, 14, 14, and 15 ELNs were selected for patients with pT1, pT2, pT3, and pT4 diseases, respectively.

Our findings robustly conclude that a minimum of 20 ELNs is essential to assess the quality of neck dissection and acquire accurate staging for patients with cN1b PTC.