Lymphatic dissemination of tumour cells and the formation of micrometastases.

Most human cancers show evidence of metastatic spread to regional lymph nodes, and the extent of lymph-node involvement is directly related to dinical outcome. Increased expression of vascular endothelial growth factor C in primary tumours is associated with increased dissemination of tumour cells to regional lymph nodes in various human carcinomas. Arguments favouring the activation of pre-existing lymphatic endothelium and the de novo formation of lymphatic capillaries (lymphangiogenesis) are discussed. We highlight recent advances in the molecular detection and characterisation of lymph-node micrometastases, as well as potential microenvironmental factors, such as chemokines, which may influence the migration and growth of metastatic tumour cells. Finally, we examine the clinical significance of lymphatic-mediated tumour-cell dissemination and the formation of lymph-node micrometastases.