Recurring lump under the armpit

Lymph nodes under the arm can enlarge while the body responds to an infection or inflammation in the arm, breast or chest. A skin cyst, irritated hair follicle or hidradenitis can also return in the same area. Less commonly, a persistent or progressive node may be linked with breast cancer or lymphoma. A lump under the armpit is a presentation of these conditions, but the lump itself does not establish the cause.

The texture, tenderness, mobility, skin changes and whether it comes and goes help a clinician decide what to examine. They may check the breast and nearby skin, review recent infections or vaccinations and arrange imaging or a sample when needed.

Book an appointment if the lump keeps returning, lasts beyond a short period, grows, feels firm or is not tender. Note when it appears, its approximate size, pain, skin changes, fever and any relation to shaving, illness or the menstrual cycle. Do not squeeze or repeatedly massage it, because this can irritate the tissue. A clinician may recommend observation, treatment for inflammation, ultrasound or a biopsy depending on the examination.

Seek prompt medical review for a lump that is enlarging, hard, fixed, present with breast skin or nipple changes, or accompanied by unexplained fever, drenching night sweats or weight loss. Seek urgent help if redness spreads quickly, the area becomes severely painful, or you feel acutely unwell. These signs call for assessment; they do not by themselves diagnose cancer.

Could this be a skin condition, infection or lymph node? Do I need breast or armpit imaging? What changes should I track while waiting? If a biopsy is advised, what will it show and when will results be discussed?