Prognostic Value of the Number of Retrieved Lymph Nodes in Pathological Nx or N0 Classical Papillary Thyroid Carcinoma.

BACKGROUND: This study evaluated the clinical implications of the number of retrieved central lymph nodes (LN) for the recurrence and recurrence-free survival (RFS) outcomes in patients with pathological Nx (pNx) or N0 classical papillary thyroid carcinoma (PTC). METHODS: In total, 464 patients were enrolled following total thyroidectomy with central LN dissection. The risk factors related to recurrence and RFS were evaluated and compared between these groups. RESULTS: Age, primary tumor size, and number of retrieved central LNs were independent risk factors for recurrence according to multivariate analysis (p < 0.05). The cut-off value for the number of retrieved central LNs related to recurrence was 4.5. Group 2 (pN0; ≥5 nodes) demonstrated a significantly higher proportion of patients with an ablation-stimulated thyroglobulin (sTg) level <2.0 ng/mL (84.9 vs 61.1 %; p < 0.050) and control sTg level <1.0 ng/mL (92.1 vs 79.6 %; p < 0.050) in comparison with patients in group 1 (pNx or pN0; 1-4 nodes). Perioperative complication rates were comparable between groups. CONCLUSION: The number of retrieved central LNs is an independent risk factor for recurrence, even among patients with pNx or pN0 classical PTC. A thorough central LN dissection may therefore improve the long-term RFS rate.