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 be produced by lymph nodes enlarged due to bacterial infections, viral infections, vaccinations, and malignancy. A breast self-examination should always include the armpit because breast cancer can enlarge the armpit lymph nodes even when the breast itself seems perfectly normal. Lymph nodes are filters that can catch malignant tumor cells or infectious organisms. When they do, lymph nodes increase in size and are easily felt.
| 
