There are many possible causes of underarm breast pain, including cysts, breast cancer, and infection. In some cases, pain may develop in relation to a woman’s menstrual cycle or due to clogged milk ducts in a woman who has given birth to a child. Sometimes, pregnant women may also experience tenderness and swelling under the arms as a normal pregnancy symptom. A rash, friction from clothing that rubs the skin, and even something as simple as an overly tight bra may cause this problem as well.
One of the most common causes of breast pain under the arm is some sort of lump. A lump that develops in this area is an abnormal growth that may be hard, rubbery, immobile, or mobile. In some cases, it may be a benign cyst or other type of non-cancerous growth, but in others, underarm breast pain may be a symptom of a cancerous breast lump.
Sometimes, hormonal or physical changes in a woman’s body can cause underarm breast pain. For example, some women experience breast tenderness, including in the underarm region, during certain parts of their menstrual cycles. In such a case, a woman’s pain may be caused by changes in the levels of progesterone and estrogen in her body. When breast pain is related to a woman’s menstrual cycle, it is often referred to as cyclic breast pain.
In some cases, a woman may experience breast pain because of pregnancy. As with menstruation, pregnancy is marked by changes in the levels of progesterone and estrogen in a woman’s body. The pain or tenderness a woman may feel in her underarm area may develop as a result of these hormonal changes. Additionally, most women experience breast growth during pregnancy, and this may be accompanied by pain and tenderness as well. Often, the pain is at its worst during the first trimester.
Underarm breast tenderness may also develop as a sign that something is wrong. Besides cancer, other issues such as infection, clogged milk ducts, and skin rashes may cause pain in this area. A woman may develop pain in the underarm as a result of friction caused by her clothing or even by a very tight bra. Additionally, trauma or injury to the breast tissue may cause pain under the arm.