pain and soreness under left arm could in be breast cancer?

I have been having pain under my left armpit breast area for about a week, I don't feel a lump or anything but it is sore and I was worried that it could be breast cancer. Can you help?

[CCF-RN,MSN-JS]

Dear Nikkimouse23, Pain under the armpit could be due to a variety of causes.  This would be an unusual presentation for breast cancer.  Discuss this with your doctor who can ask some questions and start to help determine what might be the problem.

[Nikkimouse23]

Thank you.

[ccbrew2]

I have had constant pain in my left breast, arm pit, and arm for almost a year now.  I have had a mammogram and MRI (of shoulder).  My OBGYN is convinced it is fibrocystic breasts, but I have no lumps.  My Family Dr. believes it is muscular and had me go to P.T. for a month.  Physical therapy did seem to help somewhat in the shoulder area, but not in the breast or arm.  What should my next step be in resolving this pain?

[Fran237]

A related discussion, housewife was started.