The lymphatic system

• Lymph vessels are very fine tubes that drain the fluid, called lymph, which escapes into the body's tissues. They run next to the arteries and form a network that returns the watery fluid into the bloodstream near the heart.

• Lymph nodes, sometimes called glands, are swellings that occur near to the main arteries. They act as filters for the lymph, and also have a role in the body's immune system.

• Microscopic cancer cells can escape into lymph, and can become trapped in lymph nodes. If the cells then grow, they form growths called metastases. This is one of the common ways that many cancers can spread to different parts of the body.

• Surgery for many types of cancer (including cervical, endometrial and vulval cancers) usually involves removing lymph nodes and the nearby lymph vessels.