What Does a Lump Under Your Armpit Mean?

Most lumps under the armpit are not dangerous. However, some bumps may signal a serious underlying condition, such as breast cancer or an infection.

An armpit lump or a swelling under the armpit (axilla) may result due to various reasons. 

Most causes of armpit lumps or bumps are not dangerous. However, you must consult a doctor for a definitive diagnosis. This is because some armpit lumps may be caused by serious underlying conditions.

A lump under the armpit is typically due to an enlarged lymph node (also called lymph glands or simply glands), which are spherical to oval structures present at various sites, such as the armpits, neck, chest, abdomen, and groin.

• They are a part of the lymphatic system that plays a crucial role in the immune system.
• Lymph nodes help fight infections by acting as filters that remove disease-causing organisms (including bacteria and viruses) from the lymph fluid that passes through them.
• Hundreds of lymph nodes are present in different parts of the body, and they contain clusters of immune cells (lymphocytes) that help keep you healthy.
  • There are about 20 to 30 lymph nodes present in the armpit region.

Lymph nodes are generally too small to be felt under the skin. Swollen lymph nodes (called lymphadenopathy) in the armpit (axillary lymph nodes) can cause a lump that generally occurs due to an infection or allergy.

Other causes of a lump under the armpit

• Infections, such as viral, fungal, and bacterial infections of the throat, respiratory organs, and breast, such as: 
  • Epstein–Barr virus infection,
  • cat scratch disease,
  • herpes,
  • human immunodeficiency virus infection,
  • tuberculosis, or
  • infectious mononucleosis or mono.
• Autoimmune diseases, such as:
  • rheumatoid arthritis,
  • scleroderma,
  • psoriasis,
  • systemic lupus erythematosus,
  • dermatomyositis, and
  • Sjogren’s syndrome.
• Cancers, such as:
  • leukemia,
  • lymphoma,
  • Kaposi sarcoma,
  • breast cancer,
  • lung cancer, and
  • skin cancer (melanoma).
• Hidradenitis suppurativa (painful and swollen glands)
  • Typically seen in obese children that occur due to recurrent infections or abscesses of lymph nodes in the armpit.
• Granulomatous diseases, such as sarcoidosis and silicone-induced granulomatous lymphadenitis
• Post-vaccination lymphadenopathy, such as after bacille Calmette–Guérin vaccine
• Lipoma (a lump of fatty tissue accumulated under the skin)
• Folliculitis, which is a common skin problem where the hair follicles are infected by fungi or bacteria 
• Sebaceous cyst
• Fibroadenoma
• Allergic reactions
• Reaction to medications, such as:
  • allopurinol,
  • penicillin,
  • phenytoin,
  • hydralazine, and
  • sulfonamides
• Diabetes mastopathy