Characteristics of neck level VI lymph nodes in papillary thyroid carcinoma: correlation between nodal characteristics and primary tumor.

Little is known about the pathological characteristics of metastatic and nonmetastatic lymph nodes (LNs) in papillary thyroid carcinoma (PTC). The aim of this study was to elucidate the pathological characteristics of neck level VI nodes and correlations with clinicopathological parameters. We investigated the clinicopathological features of 124 classical PTCs and characteristics of 850 dissected neck level VI LNs. Immunohistochemistry for nuclear factor-κB (NF-κB) and Ki-67 was performed on primary tumors, and correlations with nodal characteristics were investigated. Nodal metastasis at neck level VI was identified in 68 of 124 PTCs (54.8 %) and was significantly correlated with tumor size, tumor multifocality, extrathyroidal extension, and tumor stage. LN metastasis was significantly correlated with larger mean LN size (P < 0.001), larger size of the largest LN (P < 0.001), and more LNs (P < 0.001). The mean size of metastatic LNs (n = 233) was significantly larger than nonmetastatic LNs (n = 617) (P < 0.001). Primary tumor diameter significantly correlated with the largest LN size (P = 0.014, R (2) = 0.049), but not mean size or number of LNs by linear regression analysis. NF-κB and Ki-67 proliferation indexes were not significantly correlated with larger nodal size. These results suggested that characteristics of nodes and primary tumor would be useful criteria for making decisions about preoperative surveillance of nodal metastasis.