Armpit Lump: Causes, Evaluation, and When to See a Doctor

Common Causes

• Swollen Lymph Nodes – Most common; react to infection (viral, bacterial), inflammation, or malignancy.
• Breast Cancer Spread – Axillary nodes are first drainage site; evaluate with breast exam.
• Lymphoma/Leukemia – May present with painless, rubbery nodes.
• Abscess – Painful, red, warm; often from bacterial infection (hidradenitis, folliculitis).
• Lipoma – Soft, movable, painless fatty tumor; benign.
• Cyst – Epidermoid or sebaceous; may become infected.

Red Flags (Urgent Evaluation)

• Hard, fixed, non-mobile node
• Node >1.5 cm persisting >2–4 weeks
• Associated weight loss, night sweats, fever
• Breast changes (lump, skin dimpling, nipple discharge)
• Rapid growth

Diagnostic Steps

1. Clinical exam
2. Ultrasound
3. Blood tests (CBC, inflammatory markers)
4. Biopsy (FNA or excisional) if suspicious

Most armpit lumps are benign, but timely assessment rules out serious causes.