The lymphatic system is a network of tiny vessels that collect fluid and waste products from the body’s tissues.

This fluid is called lymph. Lymphatic vessels take the lymph to small glands called lymph nodes where substances that could be harmful to the body, such as bacteria or cancer cells, are trapped and removed. This helps to protect the body from infection. The lymph then passes back into the blood.

Lymph nodes are small, rounded glands that can range in size from about 1 mm to 25 mm.

There are lymph nodes all around the body, including the armpit, groin, stomach, chest and neck. The number of lymph nodes varies in different people. There are usually around 15–30 lymph nodes in the armpit.
 

Illustration of lymph nodes near the breast