Solid Lump Under the Armpit

Armpit lymph nodes can enlarge while the immune system responds to an infection or irritation in the arm, chest, or breast. A lump may also be a cyst, an inflamed hair follicle, or normal tissue that feels more prominent. Breast cancer can involve lymph nodes in the armpit, and lymphoma can also cause enlarged nodes; however, an armpit lump does not by itself establish either diagnosis. Features such as size, mobility, tenderness, skin change, and duration guide assessment.

Book a clinical examination if the lump persists, grows, feels hard or fixed, or has no clear explanation. The clinician may examine both armpits, the breasts or chest, nearby skin, and the arm. Depending on the findings, they may arrange imaging or sampling. Note when it appeared, whether it changes with illness, and any recent vaccination, skin injury, infection, or new medicine.

Seek prompt medical advice for a lump that is steadily enlarging, fixed in place, associated with breast or chest changes, or accompanied by unexplained fever, drenching night sweats, or weight loss. Get urgent help for rapidly spreading redness, severe pain, high fever, or swelling of the arm with breathing difficulty. These signs need assessment rather than observation alone.

Ask what the lump feels like on examination, which causes fit its location, and whether breast or lymph-node imaging is needed. Ask when to return if it remains, whether sampling is appropriate, and which changes should prompt earlier review.