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. Do not try to diagnose lumps without professional help. The medical history will be obtained and a physical examination performed.
Testing depends on what is found during the physical examination.
Home Care Check with your health care provider to determine the nature of the lump. For a lump in the armpit caused by an infected, painful gland, follow the instructions about the proper treatment for the underlying infection. A lump in the armpit caused by a generalized viral infection will eventually disappear without therapy. A lump in the armpit caused by an allergic reaction will go away after the provoking substance is removed. No treatment is necessary for a lump in the armpit caused by normal breast tissue, and usually no treatment is necessary for a cyst .