What should you know about a lump in the left armpit?

A lump in the left armpit can come from several tissues, so persistence, growth, feel, and breast or infection symptoms guide the next step. Enlarged lymph nodes may follow an infection or skin irritation, and cysts or inflamed glands can also form there. An armpit lump is not automatically a sign of breast cancer or lymphoma.

The armpit contains lymph nodes that drain the arm, chest wall, and breast. A recent vaccination, skin wound, shaving irritation, or infection can make a node tender or enlarged. A blocked gland, cyst, or lipoma may feel more superficial. Breast cancer can present with an armpit lump, and lymphoma can present with enlarged lymph nodes, but these conditions require assessment and are not diagnosed from location alone.

Check gently for tenderness, redness, warmth, mobility, firmness, and change. Note breast or nipple changes, arm swelling, fever, persistent tiredness, night sweating, or unexplained weight change.

Record when the lump began and any recent vaccine, infection, injury, shaving, or skin problem on that side. Do not squeeze or puncture it. Arrange a clinical examination if it persists, enlarges, feels hard or fixed, or has no clear trigger. The clinician may examine both armpits, the breast and chest wall, and nearby skin, then decide whether imaging or sampling is useful.

Seek prompt care for rapidly increasing swelling, severe pain, spreading redness, fever with marked illness, or new arm swelling. Arrange timely review for a persistent, enlarging, firm, or fixed lump, especially with a breast or nipple change, unexplained weight change, ongoing fever, or night sweats. These features determine how quickly to be seen; they do not mean that the lump is certainly cancer.

Ask whether the lump feels like a lymph node, skin lesion, or another structure, and whether both breasts and armpits should be examined. Ask which test would clarify the finding, how soon follow-up should occur, and what change should prompt earlier contact. Mention any recent vaccination, infection, injury, medicines, or previous breast or lymph-node problem.