I've just started having these same symptoms; its a soreness especially whe you lift your arm near yur beast. i thought i might be related to menopause...but nowadays it seems evertyhting is related to menopause..
Pain under the arm can be due to many things. Some causes include a pulled muscle, a lymph gland or a swelling in the breast. The tail of the breast trails off under the armpit and sometimes can be swollen. This type of pain isn't specifically a symptom of menopause, but hormonal irregularities could be causing discomfort there. If the symptom continues, see your doctor for an exam just to be sure there isn't a problem.
Machelle M. Seibel, MD