Dear sheep: Skin on the breast is like skin anywhere on the body and is subject to a variety of abnormalities. Without examination, it is impossible to speculate on a possible cause. You should see your doctor (or perhaps a dermatologist) for examination.
sorry i should have stressed it is NOT on the skin it comes from the inside underneath the skin, no rash no open skin no dry skin etc.
The nurse only responds once to a question. You might see a dermatologist though, breast cancer does not always itch, hurt, etc. I felt nothing with mine, just found it with a mammogram.