Tumor progression to invasive metastatic disease often begins with lymphatic and/or blood vessel invasion. In contrast to blood vessels, research on lymphatic vessels has lagged behind, primarily due to the lack of molecular tools capable of specifically distinguishing lymphatic endothelial cells from blood endothelial cells. It was not until recent years that the study of the characteristics of lymphatic vessels in tissues and cell culture were possible, following the discoveries of lymphatic specific markers. This book examined how lymphatic specific marker could be utilized in pathological and clinical settings in determining lymphatic vessel invasion. The in vitro models of lymphatic invasion was also highlighted in addition to the future directions of lymphatic research.