
An armpit lump usually refers to the enlargement of at least one of the lymph nodes under your arm. Lymph nodes are small, oval-shaped glands that are located throughout the body. They play an important role in your body’s immune system. The lump may feel small. In other cases, it may be extremely noticeable. Armpit lumps may be caused by cysts, infection, or irritation due to shaving or antiperspirant use. However, these lumps may also indicate a serious underlying health condition.