Definition and Function of Lymph Nodes

Lymph nodes serve an essential role in protecting the body from infection and cancer. They are located throughout the body. Here's what to know about their role in infections and cancer.

Function

Everyone has an extensive lymphatic system in their body, which consists of lymph nodes and lymph vessels. The lymph vessels carry a clear fluid called lymph that is collected from tissues throughout the body. Lymph contains cell wastes like cancer cells, bacteria, and viruses. This fluid is filtered by infection-fighting cells within the lymph nodes. These infection-fighting cells, also called white blood cells, destroy these foreign or "bad" cancer and infection-related cells. 

Location

Lymph nodes are scattered throughout the body and located in groups, like in the armpit, groin, neck, pelvis, and abdomen. In some areas like the neck, the lymph nodes are located superficially and may be palpated—they feel like a pea or small bean. In other areas, like the abdomen or the chest, lymph nodes are located deeper and cannot be felt.

Swollen Lymph Nodes and Cancer

Enlarged or swollen lymph nodes can indicate infection, cancer, or another disease that affects the immune system. Most typically, swollen lymph nodes are related to a minor infection that the immune system is fighting. For example, paratracheal lymph nodes in the neck may become swollen and tender with an ear infection, sore throat, or tooth abscess. Once the infection has cleared, swollen lymph nodes shrink back to their normal size.

Nodes that are immobile, hard, non-tender, and persistently enlarged are suspicious for cancer and should be evaluated by a healthcare provider. If cancer cells are present in a lymph node, they either spread there from the primary tumor—like a breast tumor that spreads to lymph nodes in the armpit—or they originate in the lymph node, and this is called lymphoma. If a person is diagnosed with a solid tumor, whether or not certain lymph nodes are enlarged is an important part of cancer staging, which affects how that cancer is treated.

How Lymph Nodes Are Tested

If your healthcare provider is concerned that a lymph node is affected by cancer or infection, they will take a biopsy of the lymph node or remove the entire lymph node. The contents of the lymph node can then be examined under a microscope by a pathologist to see if cancer or infection-related cells are present.

Summary

Lymph nodes play an essential role in the body's internal defenses against foreign bodies, removing waste from cells, and eliminating cancer cells. While typically small in size, enlarged or swollen lymph nodes can indicate a more serious condition, such as spreading cancer or lymphoma.

A Word From Verywell

Swollen lymph nodes do not always indicate cancer, but can indicate the body is fighting an infection. If you are feeling concerned about swollen lymph nodes, contact your healthcare provider to rule out any serious illnesses.