Patterns of Lymph Node Metastases in Papillary Thyroid Carcinoma: Results from Consecutive Bilateral Cervical Lymph Node Dissection

Abstract

In patients with papillary thyroid carcinoma (PTC), the appropriate extent of lymph node dissection has not yet been established due to lack of accurate patterns of lymph node metastases (LNM). The aim of this study was to clarify the LNM pattern in PTC patients based on our institution's experience with a consistent technique of bilateral neck dissection, and to consider the rational extent of lymph node dissection. Between 1990 and 1999, 152 consecutive patients with PTC who underwent curative total thyroidectomy and bilateral neck dissection as initial treatment were analyzed. The patterns of LNM according to clinicopathological classification were analyzed using the lymph node ratio (LNR; number of metastatic lymph nodes/number of dissected nodes) and frequency (FLNM; number of patients with LNM/number of dissected patients) in cervical compartments. Regardless of clinicopathological classification, LNR in the central compartment was consistently higher than in other compartments, and FLNM in the ipsilateral lateral compartment was consistently higher than in other compartments except for multifocal tumors. The LNR and FLNM in the contralateral lateral compartment were significantly higher in advanced (≥T3) cases than in cases with smaller tumors (T1) and were comparable to those in the ipsilateral lateral compartment in advanced (≥T3) cases. The pattern of LNR provided a better reflection of the patterns of LNM. In terms of the LNR, central neck dissection is the basic extent of lymph node dissection for all clinically apparent PTC. In advanced patients, it is also advisable to include bilateral lateral neck dissection.