Level V lymph node metastasis in N1b papillary thyroid carcinoma patients: contributing factors and pattern of metastasis

Abstract

BACKGROUND: The optimal extent of lateral neck dissection for metastatic differentiated thyroid carcinoma remains controversial given varying evidence of level V metastasis and the morbidity associated with dissection at this level. The aim of this study was to document the pattern of lateral neck metastasis and to identify risk factors contributing to level V lymph node (LN) metastasis. METHODS: A retrospective study of 396 N1b papillary thyroid cancer (PTC) patients who had undergone bilateral total thyroidectomy and lateral neck dissection at our institution between January 2009 and April 2012 was performed. RESULTS: LN metastasis was most frequent at level III (68.4%), followed by level IV (64.6%), level II (62.1%) and level V (11.95%). Multivariate analysis showed that only greater than five metastatic LNs was significantly associated with the presence of level V metastasis. The prevalence of level V metastasis was only 4.1% amongst patients with less than five metastatic LNs. The presence of level V metastasis was also associated with more overall involved nodes (24.9±15.6% vs. 14.9±11.1%, P=0.001). CONCLUSIONS: Level V nodal metastasis in PTC is uncommon and the omission of level V dissection should be considered, especially when only a single node or level metastasis is suspected. However, there is a strong indication to include level V in the lateral neck dissection when multiple LNs are present.