An armpit lump refers to enlargement of one or more lymph nodes under the arm.
Lump in the armpit; Localized lymphadenopathy - armpit; Axillary lymphadenopathy; Axillary lymph enlargement; Lymph nodes enlargement - axillary; Axillary abscess
Lumps in the armpit have various causes. Cysts and infections on the surface of the skin of the armpit may be caused by shaving or use of antiperspirants (as opposed to deodorants). This occurs most frequently in adolescents just beginning to shave. Abscesses under the skin may also produce large, painful lumps in the armpit.
Lumps may occur when lymph nodes are swollen due to bacterial or viral infections, vaccinations, and cancer.
Lymph nodes are filters that can catch infectious organisms or cancerous tumor cells. When they do, lymph nodes increase in size and are easily felt. An armpit lump in a woman should be checked by a health care provider immediately, as it may be a sign of breast cancer.
A lump in the armpit caused by a viral infection will eventually disappear without treatment. A lump in the armpit caused by an allergic reaction will go away after the "trigger" is removed. No treatment is necessary for a lump in the armpit caused by normal breast tissue. Usually, no treatment is necessary for a cyst.
A lump in the armpit caused by a lipoma is harmless, unless it grows so large that it causes discomfort.
The outlook for cancerous lumps depends on the specific type of cancer. See the following for more information:
Armitage JO. Approach to the patient with lymphadenopathy and splenomegaly. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 171.
Tower RL II, Camitta BM. Lymphadenopathy. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 484.
Linda Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.