Background and Purpose: The extracapsular spread (ECS) of lymph node metastasis (LNM) reflects tumor aggressiveness and is associated with poor survival and risk of distant metastasis. In this study, we aimed to explore the prognostic significance of epithelial-mesenchymal transition (EMT) of ECS tumors in LNM of head and neck cancers. Methods: We collected LNM samples from head and neck cancer patients (follow-up >2 years) and made 20 ECS(-): ECS(+) pairs (1:2) of LNM (N = 60), matched by the primary sites and by T and N classifications. Immunostaining of cytokeratin, E-cadherin, vimentin, and CD31 were performed and quantified to determine the epithelial-mesenchymal transition percent (EMT%), defined as vimentin(+)/cytokeratin(+) area of ECS. Univariate and multivariable analyses of clinic-pathologic factors, including EMT% of ECS, were conducted to identify the significant prognosticators. In addition, the anatomical relationship between CD31 vessels and ECS tumors was analyzed. Results: Rather than the presence of ECS in LNM, higher EMT% (>50 %) of ECS strongly correlated with the worse overall and disease-free survival and had more frequent recurrence and distant dissemination in their clinical courses. ECS tumors intermingled closely with Ki-67(-) CD31(+) non-proliferating perinodal blood vessels. Particularly, vimentin(+) ECS areas exhibited a higher density of CD31(+) perinodal vessels than did vimentin(-) ECS. Conclusion: High EMT scores of ECS tumors in LNM predict an unfavorable prognosis and systemic dissemination more accurately than the simple presence of ECS in LNM in head and neck cancer patients.
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