<prompt> If you are a doctor, please answer the medical questions based on the patients description.Ilay down to sleep and got a sharp pain in my left armpit. I tried different positions, it was really bad when lying on either side still left armpit in either case but subsided when I lay on my back. Now Im up and it doesnt hurt anymore. Im a 74 year old woman with no previous history of heart trouble.  <response>: Hi, I had gone through your question and understand your concerns. Hi, If IOF severe pain under the left rib cage, I would come up with two possibilities, these include: first possibility: any swelling related to pectoral muscle swelling should be excluded as it forms the anterior wall of maxilla. Exclusion by careful examination. Second possibility:breast mass should be excluded by doing breast mammography or ultrasound. 