Tumour. Illustration of a growth of malignant (cancerous) cells in human tissue. A lymph vessel (green) and nodes (ovoid) and a blood vessel (red) are also seen. The tumour is promoting the formation of new blood vessels, a process known as angiogenesis. The tumour cells release angiogenic growth factor proteins that bind to endothelial cells in nearby blood vessels and encourage the growth of new blood vessels from the existing ones. These blood vessels provide the tumour with oxygen and nutrients. For a sequence showing the growth of the tumour see images C048/8862 to C048/8866.