Tender armpit lump: what to know

The armpit contains lymph nodes, sweat glands, hair follicles, skin, nerves, and blood vessels. A nearby skin infection, shaving irritation, an inflamed cyst, or an immune response can make tissue sore and swollen. A breast lump or breast cancer can present with an enlarged node in the armpit, while lymphoma can involve lymph nodes; a lump alone cannot identify its cause.

Note when the lump appeared, whether it changes in size, and whether the skin is red or warm. Avoid squeezing it and pause shaving or products that irritate the area. Arrange a clinical examination if it does not settle, returns, or is difficult to move. The clinician may examine the breast, chest wall, arm, and nearby lymph nodes and decide whether imaging or another test is useful.

Seek prompt medical care for a rapidly enlarging lump, spreading redness, severe pain, fever, pus, unexplained weight loss, drenching night sweats, or a new breast or nipple change. Urgent help is appropriate if swelling is accompanied by trouble breathing, faintness, or sudden widespread illness.

Ask what structures may be swollen, whether the breast and nearby lymph nodes need examination, how long observation is reasonable, and which changes should trigger an earlier review.