The role of lymphangiogenesis in lymphatic tumour spread of urological cancers.

Metastases to regional lymph nodes are a common early event in many malignant diseases and have a poor prognosis, including in urological cancers. Molecular pathways contributing to lymphatic tumour dissemination and lymph node metastasis remain poorly understood. Besides the process of lymphovascular invasion (LVI), recent studies suggested de novo lymphatic vessel formation (i.e. lymphangiogenesis) as a potential mechanism of lymphatic tumour spread. Specific markers for lymphatic endothelium have recently been discovered, enabling basic morphological studies on lymphatic vessel density. There is a gap in the knowledge of the functional relationship between tumoral lymphatic vessels, LVI, lymphangiogenesis and the formation of lymph node metastases. The identification of lymph-specific growth factors (e.g. vascular endothelial growth factor-C and -D) as promoters of lymphatic metastasis has resulted in the interesting idea of targeting the pathways involved in lymphatic tumour progression. We summarize preliminary evidence on the role of lymphangiogenesis during the formation of lymphatic metastasis in the most common urological cancers.