Soft lump under the armpit: what to know

The armpit contains lymph nodes, sweat glands, hair follicles, fat, and other soft tissue. A tender lump may follow a skin infection, shaving irritation, a boil, or an infection in the arm or chest. A node may enlarge while the immune system responds. A persistent armpit lump can also be a presentation of breast cancer or lymphoma, but a lump cannot determine its own cause. Its texture, mobility, tenderness, duration, and relationship to nearby skin or breast changes all help guide assessment.

Book a clinical review when a lump does not settle, keeps returning, becomes larger, or has no obvious trigger. Record when it appeared and whether it is painful or attached to the skin. Tell the clinician about fever, recent vaccination or infection, cuts on the arm, breast or nipple changes, and any previous cancer history. Do not repeatedly squeeze it. Examination may be followed by imaging or a tissue sample when the findings call for it.

Seek urgent care for rapidly spreading redness, severe pain, high fever, feeling faint, or swelling that interferes with arm movement or breathing. Arrange prompt assessment for a firm or fixed lump, progressive enlargement, skin dimpling, nipple changes, or an armpit lump with persistent night sweats or unexplained weight loss.

Does this feel like a lymph node, skin lesion, or another mass? Do I need breast or armpit imaging? What changes should I report before the next appointment?