Question

Explain how cancer cells use the lymphatic system to metastasize to other organs.

Answer 1

The physiological function of lymphatic vascular networks in the body is to collect extravasated fluid, macromolecules and leukocytes at regional lymph nodes for immune surveillance, and then transport them to the blood vessels for circulation.Lymphatic microvessels consist of a thin endothelium, which is usually sparsely coated with pericytes and vascular smooth muscle cells (VSMCs).Although accumulating evidence shows that intratumoural lymphatic networks are vital for lymphatic metastasis, little is known about possible structural and functional differences between healthy lymphatic vessels and those present in tumours. Tumour blood vessels usually consist of disorganized, leaky and tortuous vasculatures, indicating that tumour lymphatic capillaries might have similar characteristics. Recent studies demonstrate that peritumoural and intratumoural lymphatic networks also consist of disorganized microvessels that might lack drainage function. The structural irregularity and leaky features of tumoural lymphatic vessels might make them more susceptible for invasion by malignant cells.In addition, lymphatic endothelial cells (LECs) of tumour-associated lymphatic networks have been reported to interact with tumour cells and to facilitate their transmigration through the endothelium.