Lymph nodes are part of your lymphatic system, which helps fight infection and cancer. Lymph nodes are pea-sized collection points that filter out germs and cells from lymph fluid. Lymph nodes are located throughout your body, but many are clustered in your neck, under your arms, and in your groin. They swell when your body has an infection or cancer.
The cause of the swelling is usually a nearby skin or tissue infection or a harmless virus that goes away on its own
Sometimes the cause is a more serious infection or cancer
Swollen lymph nodes may hurt, or they may be painless
Sometimes your doctor may do tests for certain infections or cancers
If the swelling in your lymph nodes doesn't go away in 3 or 4 weeks, doctors may do a biopsy (taking out part of the tissue to look at under a microscope)
People call swollen lymph nodes "swollen glands," but lymph nodes aren't really glands.
There are many causes of swollen lymph nodes. The most common causes are:
More dangerous causes of swollen lymph nodes are:
Normally, your body's immune defenses kill any live germs that get into your lymph nodes. But sometimes a few germs survive and cause an infection. An infected lymph node hurts, and the skin over it turns red.
Cancer cells often break off from a cancer and travel through lymph vessels to nearby lymph nodes. For example, breast cancer often spreads to the lymph nodes in the armpit that's on the same side as the cancer. Sometimes your immune defenses kill the cancer cells. But sometimes the cancer cells grow in your lymph nodes. Cancer usually makes lymph nodes very hard and stuck together.
However, probably less than 1% of people with swollen lymph nodes have cancer.
Not every person with swollen lymph nodes needs to go to a doctor right away.
See your doctor right away if a lymph node is:
Call your doctor if you have any of these other warning signs:
A lymph node that is very large (an inch or more across the middle)
A lymph node that feels hard, like a stone
Risk factors for HIV infection (such as being stuck with a needle used by another person or doing high-risk sexual activities)
Risk factors for tuberculosis (such as living or working with a person who has tuberculosis or having recently moved from an area where tuberculosis is common)
Unexplained weight loss
The doctor will decide how quickly you need to be seen based on the warning signs and other symptoms.
If you have no warning signs and you feel well, you can wait a week to see if the node returns to normal before calling your doctor.
Your doctor will ask questions about your symptoms and warning signs and will examine you. If you clearly have a harmless problem, doctors will wait and see whether the lymph node swelling goes away. Otherwise, doctors will do tests based on what they think is causing your swollen lymph nodes. Tests may include: