Hi.
Nipple discharge can be caused by both benign and malignant conditions. This is especially true when it involves only one breast. Benign causes include fibrocystic disease, intraductal papilloma, and duct ectasia. Malignant causes include breast carcinoma, breast sarcoma, and Paget’s disease of the nipple.
I agree with the previous post. I strongly urge you to consult your doctor regarding the problem in your left breast.
Take care.
Yes you need to have a doctor look at that. I had that problem four years ago it was not black but the doctor did take a sample.That is something that you have to be seen about ,if you are not comfortable with the answers then there are other doctors.You can ask you regular doctor to find a breast specialist in your area.