What is an underarm lump?

An underarm lump generally refers to swelling or enlargement of one of the axillary lymph nodes located under the arm (armpit). Lymph nodes are very small clusters of immune cells that are an important part of the body’s lymphatic system, which is a part of the immune system. Your body relies on the lymphatic system to fight off germs, infections, and abnormal substances, such as cancer cells.

There are more than 600 lymph nodes throughout the body, but the ones most frequently enlarged or swollen are found in the neck, under the chin, under the arms, and in the groin. An enlarged lymph node under your arm can result from infection, malignancy, and autoimmune disorders.

Swollen lymph nodes are also known as lymphadenitis, lymphadenopathy, swollen nodes, or swollen glands. They can occur in any age group or population, but generally occur most often in children.

An underarm lump due to a viral infection often gets better on its own. However, some infections that are caused by bacteria or other pathogens need medical attention. An underarm lump can also be a sign of breast cancer. Seek prompt medical care if an underarm lump has been present for more than two weeks, is growing, or is red, tender, hard, or irregular in shape.


What other symptoms might occur with an underarm lump?

An underarm lump often occurs with other symptoms that vary in severity depending on the underlying disease, disorder or condition. For example, an underarm lump due to an infectious disease may be sore and painful to touch and occur with a fever and body aches.

Symptoms that may occur along with... Read more about underarm lumpsymptoms


What causes an underarm lump?

The most common cause of an underarm lump is a localized infection in the breast, arm, or the armpit itself, such as folliculitis due to an infected hair follicle. Immune system disorders and some types of cancer, such as breast cancer, can also lead to an underarm lump due to swollen lymph nodes.

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Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Aug 11, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Allergies and the Immune System