Should level V be included in lateral neck dissection in treating papillary thyroid carcinoma?

BACKGROUND The study was designed to explore the regular patterns of level V lymph node metastasis (LNM) in papillary thyroid carcinoma (PTC), and to indicate whether level V should be included in the management of lateral neck dissection when treating PTC. METHODS This retrospective study consisted of 330 patients diagnosed with PTC from January 1994 to July 2009 who underwent an operation that included therapeutic lateral neck dissection (levels II to V). The patterns of lateral neck LNM were analyzed and the relevant risk factors of level V LNM were analyzed with univariate and multivariate analysis, respectively. RESULTS All the patients underwent lateral neck dissection at levels II to V. The predominant site of metastasis was level III (247/330 (74.8%)), followed by level IV (233/330 (70.6%)), and level II (215/330 (65.3%)). Simultaneous multilevel involvement (level II, III, and IV) of lymphatic metastases presented in 46.1% (152/330) of the cases. Level V showed 28.8% (95/330) of nodal metastasis. Multivariate analysis showed that level V LNM was significantly associated with location (whole thyroid), gross extrathyroidal extension and simultaneous multilevel involvement (level II, III and IV). (P <0.05). CONCLUSIONS Due to relatively high rate of level V involvement and its correlation with location (whole thyroid), gross extrathyroidal extension and multilevel involvement, we consider that it may be more rational to include level V in the therapeutic lateral neck dissection when treating PTC, especially for those who have any one of these three independent risk factors.