An Overview of Lymph Nodes

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A lymph node, sometimes referred to as a lymph gland, is 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 and viruses. Swollen lymph nodes are a sign that the body is fighting an infection or disease. Some diseases can also directly affect lymph nodes, including cancers like lymphoma.

This article explains the structure and function of lymph nodes as well as the different types of lymph nodes situated throughout the body. It also describes conditions that can affect lymph nodes and when it is time to see a healthcare provider.

Doctor examining older man's lymph nodes

dardespot / Getty Images

Lymph Node Structure

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 that can do the body harm.

In addition to lymph nodes, lymphatic fluid (lymph), 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 around 600 located throughout the body, many of which are clustered in the armpit, groin, and neck.

What Do Lymph Nodes Do?

The primary function of lymph nodes is to filter lymphatic fluid to isolate and kill foreign invaders that cause infection or disease. To do this, lymph nodes contain specialized white blood cells called lymphocytes that activate the immune defense in different ways:

The activation of the immune system triggers a defensive response known as inflammation. Inflammation causes blood vessels will dilate (widen) to allow larger immune cells access to the site of the infection. It also generates heat that helps damage and destroy the invader.

Together, these effects cause lymph nodes to become red, swollen, and warm—a condition referred to as lymphadenopathy or adenopathy. Once the foreign invader has been neutralized, the lymph node will return to its normal state.

How to Check For Swollen Lymph Nodes

Lymph nodes are strategically clustered throughout the body. Some are situated near the surface of the skin and can be easily felt (such as in the groin or armpit, under the jaw, or behind the ear). Others are located deep inside the body (such as in the chest and abdominal cavity) and cannot be readily felt.

If lymphadenopathy is severe, it can cause firm lumps anywhere from 1 to 3 inches in size. Those near the surface may be red, warm, and tender to the touch. Some can cause extreme pain, especially those behind the ear that can compress the Eustachian tube and adjacent structures.

However, not all swollen lymph nodes are painful or readily noticed. If an infection is relatively mild or localized, you might only find the swollen lump by accident when showering.

The same is true for certain chronic infections like HIV that can cause persistent, low-level inflammation. It is not uncommon to find one in the armpit or neck and have no other symptoms.

A lymph node can also be visibly swollen but entirely painless. This is often the case when the lymph node itself is subject to disease. This can occur with cancers like lymphoma or non-cancerous diseases like sarcoidosis that can cause the node to become hard, immovable, and painless.

Swollen lymph nodes that are movable are more likely to be benign (non-cancerous).

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This video has been medically reviewed by Benjamin F. Asher, MD

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, a cancer specialist known as an oncologist can usually 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.

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.

Causes of Swollen Lymph Nodes

There are many conditions that can directly or indirectly affect the lymph nodes. Some are relatively mild and treatable, while others are more serious.

Infections

Lymphadenopathy can be caused by infections that are acute (sudden and short-lasting) or chronic (persistent or recurrent).

If an infection is acute, the symptoms may be more noticeable due to the rapid rise of inflammation. If the infection is chronic, symptoms may be less apparent because the underlying inflammation will generally be lower. But the opposite can also be true in both cases.

Some of the more common infections associated with lymphadenopathy include:

Cancers

Lymphadenopathy can occur with any cancer as cancer cells break off and get trapped by nearby lymph nodes.

For instance, people with breast cancer will typically get swollen lymph nodes in the adjacent armpit, while people with lung cancer will typically experience lymphadenopathy in the chest cavity.

Most escaped cancer cells are killed in the lymph nodes before they can start growing elsewhere. But sometimes the lymph nodes are unable to contain the cells and are overtaken by cancer. When this happens, the cancer can spread to other parts of the body (known as metastasis).

Additionally, there are certain cancers that start in lymph nodes or affect lymphocytes, the most common of which include:

Immune Disorders

Autoimmune diseases are those in which the immune system mistakenly attacks normal cells and tissues. In some cases, the immune assault directly targets lymph nodes. At other times, the inflammation caused by the immune assault can affect nearby lymph nodes.

Autoimmune disorders known to cause lymphadenopathy include:

Another disease thought to involve autoimmunity, called sarcoidosis, can also cause swollen lymph glands. It belongs to a group of granulomatous diseases that cause hardened granules in organs. If the lymph nodes are affected, they will often be stone-like and matted (melded in clusters).

Medications

Certain medications can also cause lymphadenopathy either by triggering an immune response or an allergic or inflammatory reaction.

Common examples include:

  • Bactrim (trimethoprim/sulfamethoxazole)
  • Zyloprim (allopurinol)
  • Tenormin (atenolol)
  • Capoten (captopril)
  • Tegretol (carbamazepine)
  • Apresoline (hydralazine)
  • Penicillin
  • Dilantin (phenytoin)
  • Mysoline (primidone)
  • Daraprim (pyrimethamine)
  • Quinidine

COVID-19 vaccine has also been known to induce lymphadenopathy, typically in the armpit nearest the injection site.

common causes of a swollen lymph node

Verywell / Brianna Gilmartin

When to See a Healthcare Provider

Swollen lymph nodes are common. In many cases, they will resolve once an underlying infection clears, often within a few days to a week. If the condition persists or is severe, you should have it looked at.

You should see a healthcare provider if:

  • Swollen lymph nodes last for more than two weeks.
  • The swollen lymph nodes are painless.
  • The lymph nodes are hard and unmovable.
  • The lymph nodes continue to grow in size. Anything over 1 inch is never normal.
  • The swelling is accompanied by persistent fever, night sweats, or weight loss.

If cancer is suspected, the healthcare provider can order a lymph node biopsy to obtain a small sample of fluid and tissues using a needle and syringe. The sample can then be checked in the lab for cancer cells.

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. Cancer can also affect lymph nodes either as it spreads from a tumor or starts in the lymph nodes themselves (lymphoma).

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By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."