An armpit lump refers to enlargement of one or more lymph nodes under the arm.

Lumps in the armpit have various causes. Cysts and infections on the surface of the skin of the armpit may be caused by shaving or use of antiperspirants (as opposed to deodorants). This occurs most frequently in adolescents just beginning to shave. Abscesses under the skin may also produce large, painful lumps in the armpit.

Lumps may occur when lymph nodes are swollen due to bacterial or viral infections, vaccinations, and cancer.

Lymph nodes are filters that can catch infectious organisms or cancerous tumor cells. When they do, lymph nodes increase in size and are easily felt. An armpit lump in a woman should be checked by a health care provider immediately, as it may be a sign of breast cancer.

• Bacterial infection
  • Arm or breast infection
  • Cat scratch disease
  • Ascending lymphangitis
  • Lymphadenitis
• Cancer
  • Hodgkin's lymphoma
  • Leukemia
  • Non-Hodgkin's lymphoma
• Fungal
  • Sporotrichosis
• Other
  • Benign (harmless) cyst
  • Lipomas (harmless fatty growths)
  • Normal breast tissue (breast tissue extends into the armpit area)
• Vaccinations
  • Allergic reaction possibly caused by sulfa drugs, iodine, or penicillin
  • Measles, mumps, rubella vaccine (rare)
  • Smallpox vaccination
  • Typhoid vaccine
• Viral infection
  • AIDS
  • Chickenpox
  • Infectious mononucleosis
  • Shingles (herpes zoster)