<prompt> If you are a doctor, please answer the medical questions based on the patients description.Hi doctor, I have been having some pain and soreness in my breast, and recently I noticed a lump or mass in my arm. What could be the problem?  <response>: Based on your symptoms, it is possible that you have a breast cyst. This is a noncancerous fluid-filled sac that can develop in the breast tissue and sometimes cause pain or discomfort. The lump in your arm could be a swollen lymph node, which can sometimes be related to breast cysts. 