N Stage: Controversies and Recent Issues

Min, Hye Sook

Abstract

The current TNM staging including N staging has been suggested as a gold standard for the appropriate therapy in the well differentiated thyroid cancer patients. N staging was established based on histopathologic findings, however, the newly suggested prognostic factors for the revision of N staging include some clinicopathologic factors, such as clinical metastasis (macrometastasis), large node metastasis (> or =3 cm), extranodal extension and the number of metastatic node. Recently, American Thyroid Association reported the possibility that the low-risk group patients would be overestimated as high-risk group patients that leads to the overtreatment, the following unnecessary complication and the economic cost. The preexisting N1a/N1b classification by anatomical location of metastatic node still remains as a strong prognostic factor; however, many evidences indicated that the clinicopathologic factors described above should be considered in the risk stratification in the near future. Thus, it needs to be stressed that the four factors of micrometastasis, large node metastasis (> or =3 cm), gross or microscopic extranodal extension and multiple metastatic node (>5 cm) have been established as negative or positive prognostic factors and should be noted in clinical practice.