Prognostic value of lymphatic and blood vessel invasion in neuroendocrine tumors of the lung.

Few data on the influence of vessel invasion on the progression of neuroendocrine lung tumors are available. Because of the lack of specific markers, previous studies could not reliably discriminate lymphatic and blood vessels. By immunostaining for podoplanin, specific for lymphatic endothelium, and CD34 antigen, we assessed lymphatic and blood vessel invasion in 120 tissue specimens of patients with neuroendocrine lung tumors. Lymphovascular invasion was correlated with clinicopathologic parameters, and its prognostic relevance was evaluated. Lymphatic vessels were identified exclusively at the tumor invasion front, whereas blood capillaries were also seen within tumors. Lymphatic vessel as well as lymphatic and blood vessel invasion was prevalent in patients with high-grade neuroendocrine tumors and advanced tumor stages, closely associated with lymph node metastases (P < 0.0001). In univariate analysis, these two invasion types correlated with decreased disease-free survival (both P < 0.0001), whereas blood vessel invasion alone did not. In multivariate analysis, only tumor grade and lymph node status remained statistically significant factors for prognosis (P = 0.016 and P < 0.0001). Our results suggest that evaluation of lymphatic vessel invasion is important in neuroendocrine lung tumors serving as a prognostic parameter for disease-free survival.