Lymph fluid normally flows through a network of lymph vessels. These lymph vessels connect to a group of lymph nodes. The nodes act as a filter. They trap or destroy anything harmful that the body does not need.
Inside the lymph nodes are white blood cells, also called lymphocytes. These white blood cells attack and break down bacteria, viruses, damaged cells or cancer cells.
The lymph fluid carries the waste products and destroyed bacteria back into the bloodstream. The liver or kidneys then remove these from the blood. The body passes them out with other body waste, through bowel movements (poo) or urine (pee).
Lymph nodes sometimes trap bacteria or viruses that they cannot destroy straight away. For example, they may do this when you have an infection. When the lymph nodes are fighting the infection, they often swell and become sore to touch.
Sometimes cancer cells spread from where a cancer started (the primary site) to other parts of the body. They can travel around the body in the blood or through lymph fluid. When these cancer cells reach another part of the body, they may grow and form another tumour. This is called a secondary cancer or a metastasis.
Cancer cells can sometimes spread into the lymph nodes from a cancer somewhere else in the body. This is called secondary cancer in the lymph nodes. Cancer can also start in the lymph nodes themselves. This is called lymphoma. If there is cancer in the lymph nodes, they may swell, but are usually painless.
There are different causes of swollen lymph nodes. But if you notice a painless, swollen lymph node, it is important to get it checked by your GP.
The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels that make and move lymph from tissues to the bloodstream. The lymph system is a major part of the body's immune system.
Lymph is a clear-to-white fluid made of:
- White blood cells, especially lymphocytes, the cells that attack bacteria in the blood
- Fluid from the intestines called chyle, which contains proteins and fats
Lymph nodes are soft, small, round- or bean-shaped structures. They usually cannot be seen or easily felt. They are located in clusters in various parts of the body, such as the:
- Neck
- Armpit
- Groin
- Inside the center of the chest and abdomen
Lymph nodes make immune cells that help the body fight infection. They also filter the lymph fluid and remove foreign material such as bacteria and cancer cells. When bacteria are recognized in the lymph fluid, the lymph nodes make more infection-fighting white blood cells. This causes the nodes to swell. The swollen nodes are sometimes felt in the neck, under the arms, and groin.
The lymph system includes the:
- Tonsils
- Adenoids
- Spleen
- Thymus
Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW. Lymphatic system. In: Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW, eds. Seidel's Guide to Physical Examination. 9th ed. Philadelphia, PA: Elsevier; 2019:chap 10.
Hall JE, Hall ME. The microcirculation and lymphatic system: capillary fluid exchange, interstitial fluid, and lymph flow. In: Hall JE, Hall ME eds. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 16.
Updated by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Lymph nodes, sometimes referred to as lymph glands, are an important part of the immune system. Lymph nodes are clustered throughout the body and function as filters, removing foreign particles from fluids that run through the vessels of the lymphatic system.
Within lymph nodes are white blood cells called lymphocytes that help neutralize foreign agents like bacteria. Swollen lymph nodes are a sign that the body is fighting infection, and they may be tender and painful. In some cases, swollen lymph nodes may be a sign of cancer.
This article describes lymph node structure and function, and the types of lymph nodes found throughout the body. It lists some conditions that can affect them and offers information about when you should contact a healthcare provider about a swollen lymph node.
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Lymph nodes are small, bean-shaped organs that are part of the lymphatic system. The lymphatic system is a network of vessels and organs that isolate and neutralize foreign agents and particles that can do the body harm.
In addition to lymph nodes, lymphatic fluid, and lymphatic vessels, the system is comprised of the thymus gland, tonsils, spleen, and bone marrow.
Lymph nodes vary in size from a few millimeters to up to 2 centimeters in diameter. There are hundreds located throughout the body, but they are mainly clustered in certain parts of the body.
Lymph Node Function
Lymph nodes work to identify and filter out foreign agents that cause infections. To do this, lymph nodes contain two different types of white blood cells:
- B lymphocytes (B cells) that produce antibodies to help fight bacteria, viruses, fungi, and other infectious agents
- T lymphocytes (T cells)that launch the adaptive immune response (an immune response specific to an infectious agent)
When a foreign agent has been trapped and the immune defenses are activated, the body will respond with inflammation. This causes the lymph nodes to swell.
Swollen lymph nodes, referred to as lymphadenopathy, can often be felt and seen, but not always. Some may be painful; others are not.
Not every particle that is filtered by the lymph nodes can be neutralized. One example is cancer cells that are shed from a nearby tumor. Even though lymph nodes cannot kill the cancer cells, they may be able to isolate and contain them during the early stages of the disease.
When to See a Healthcare Provider
Lymph nodes may remain swollen for up to two weeks. If they don't get better or keep getting bigger, contact your healthcare provider.
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Types and Locations
Lymph nodes are clustered throughout the body in key locations. These include the armpits, neck, groin, upper abdomen, and mediastinum (the area between the lungs that contains all the principal organs of the chest).
Swollen lymph nodes in the armpits, neck, and groin can often be felt. Those in the mediastinum and upper abdomen may only be revealed with imaging tests such as a computed tomography (CT) scan or ultrasound.
The types and locations of lymph nodes vary as follows:
Cervical Lymph Nodes
Cervical lymph nodes are those in the neck. They are further broken down by their location:
- Anterior cervical lymph nodes are those nearest the front of the neck. These typically swell when you have a cold or strep throat.
- Posterior cervical lymph nodes are located behind the band of muscles on the side of the neck. These often swell when you have infectious mononucleosis.
- Occipital lymph nodes are located at the back of the neck at the base of the skull. These often swell with infections like HIV.
Axillary Lymph Nodes
Axillary lymph nodes are the lymph nodes located in the armpit (axilla). There are usually between 10 and 40 lymph nodes in the axilla.
The axillary lymph nodes are important in the diagnosis of breast cancer. When cancer cells are shed from a breast tumor, they first travel to the axillary nodes. Because cancer cells tend to spread through lymph nodes in a specific pattern, doctors can often tell how advanced the cancer is.
Supraclavicular Lymph Nodes
Supraclavicular lymph nodes are located just above the collarbone (clavicle). Most of the time, the enlargement of supraclavicular lymph nodes is a sign of a serious disease such as lung cancer or lymphoma (a type of blood cancer).
Mediastinal Lymph Nodes
Mediastinal lymph nodes reside in the center of the chest cavity between the lungs. People cannot feel mediastinal lymph nodes, but they can be seen in imaging studies such as a CT scan or positron emission tomography (PET) scan.
Checking mediastinal lymph nodes is essential to the staging of lung cancer and some lymphomas.
Inguinal Lymph Nodes
Inguinal lymph nodes are located in the groin. Because they are responsible for filtering lymphatic fluids from the feet to the groin, they can become swollen for many reasons. These include injuries, sexually transmitted diseases, skin infections, yeast infections, and cancer.
Retroperitoneal Lymph Nodes
Retroperitoneal lymph nodes are situated at the back of the abdomen behind the tissues that cover the abdominal wall. These are the nodes to which testicular cancer first spreads. They can only be seen in imaging studies.
Mesenteric Lymph Nodes
Mesenteric lymph nodes lie deep within the abdomen in the membranes that surround the intestine. These nodes often become swollen due to gastroenteritis (stomach flu) but are also sometimes affected by inflammatory bowel disease (IBD) and lymphoma.
Pelvic Lymph Nodes
Pelvic lymph nodes are situated in the lower abdomen in the area that contains the hip bones, bladder, rectum, and reproductive organs. Pelvic lymph nodes are only seen in imaging studies. Swollen pelvic lymph nodes may be a sign of bladder, prostate, cervical, ovarian, or anal cancer.
Where Lymph Nodes Are Located
Lymph nodes are classified by their location, including:
- Axillary lymph nodes (armpits)
- Cervical lymph nodes (neck)
- Inguinal lymph nodes (groin)
- Mediastinal lymph nodes (in the chest cavity)
- Pelvic lymph nodes (in the pelvis)
- Retroperitoneal lymph nodes (back of the abdomen)
- Supraclavicular lymph nodes (above the collarbone)
Associated Conditions
There are many conditions that can directly or indirectly affect the lymph nodes. Some are relatively mild and treatable, while others are more serious.
Lymphadenopathy
Lymphadenopathy, or the swelling of lymph nodes, is not a disease but a symptom of a disease. Based on its location and features, lymphadenopathy can reveal a lot about what is going on inside the body.
The features of lymphadenopathy may be described as:
- Mobile vs. fixed: Mobile lymph nodes are those that can be easily moved, while fixed lymph nodes are stuck to an internal structure. Mobile nodes are generally benign (non-cancerous), while fixed nodes are commonly seen with cancer.
- Painful vs. non-painful: Tender lymph nodes generally occur with infections, while cancerous nodes are typically non-tender.
- Localized vs. generalized: Localized lymphadenopathy, which affects one part of the body, is often due to a local infection such as strep throat. Generalized lymphadenopathy, affecting many parts of the body, can occur with autoimmune diseases, cancer, or drug reactions.
Verywell / Brianna Gilmartin
Lymphadenitis/Lymphangitis
Lymph nodes can "catch" viruses and bacteria but are also susceptible to infections themselves.
- Lymphadenitis is the enlargement in one or more lymph nodes, usually due to an infection.
- Lymphangitis is inflammation of lymphatic vessels, mainly due to an infection, that can involve lymph nodes as well
One such example is a bacterial infection from cats called cat scratch fever. The disease can cause swollen lymph nodes that last for months as well as fever, muscle aches, and nausea.
Cancer
Lymph nodes are commonly involved with cancer, but their role differs based on whether a solid tumor or lymphoma is involved.
With solid tumors such as breast cancer, cancer cells usually travel to nearby lymph nodes before metastasizing (spreading to other parts of the body).
Solid tumor cancers are typically staged based on the TNM system. The TNM system describes the severity of the disease based on the size of the tumor (T), the number and location of lymph nodes with cancer (N), and the presence or absence of metastasis (M).
With lymphoma, cancer starts in the lymph nodes. When lymphomas spread to other parts of the body, it is not referred to as metastasis but rather as "extranodal involvement."
Lymphoma is staged based on the number and location of affected lymph nodes, whether one or both sides of the body are involved, and if there is extranodal involvement.
Conditions Affecting Lymph Nodes
Conditions that directly or indirectly affect the lymph nodes include:
- Lymphadenopathy: Swollen lymph glands causes by the presence of an infection or disease somewhere in the body
- Lymphadenitis: Swollen lymph nodes caused by an infection of the lymph nodes
- Lymphangitis: Inflammation of lymphatic vessels that can also affect the lymph nodes
- Cancer: Either caused by the spread of cancer to a lymph node or by a cancer that starts in the lymph nodes (lymphoma)
Summary
Lymph nodes are small, bean-shaped organs that support the immune system by trapping foreign agents and killing them. They do so by filtering bacteria, viruses, and other disease-causing agents circulating in the lymphatic system. White blood cells, called lymphocytes, are then recruited to control infection.
Lymph nodes are clustered throughout the body, including the neck (cervical lymph nodes), groin (inguinal lymph nodes), and armpits (axillary lymph nodes). There are internal lymph nodes in the abdomen (mesenteric and retroperitoneal), chest cavity (mediastinal), and lower abdomen (pelvic).
Swollen lymph nodes
(lymphadenopathy) can occur in response to an infection or disease in any part of the body. When a lymph node is infected and becomes swollen, it is referred to as lymphadenitis. Cancer can also affect lymph nodes either as it spreads from a tumor or starts in the lymph nodes themselves (lymphoma).
Frequently Asked Questions
Where are my lymph nodes?
There are about 600 lymph nodes spread throughout the body, such as in the neck, behind the ear, in the legs, and in the abdomen. The major clusters of lymph nodes are in the armpit, groin, and neck.
Why do lymph nodes get swollen?
Swollen lymph nodes are a sign that your body is fighting an infection. When a virus or bacteria gets trapped inside a lymph node, white blood cells called lymphocytes aggressively attack. The resulting inflammation causes the lymph nodes to enlarge.
Lymph nodes can also become enlarged if cancer cells spread to them and grow.
What do cancerous lymph nodes feel like?
Cancerous lymph nodes tend to be enlarged, painless, and feel rubbery when pressed. They are usually fixed rather than moveable.