Could be anything. Might be some sort of skin disorder/infection that needs treatment? However, redness or a rash on the skin and/or around the nipple is a change that women are warned to look out for and report to their doctor.
I have had breast cancer in my left breast and had a mastectomy. I've had a reddish pink patch above my left nipple which is getting bigger. It doesn't itch and there is no lump. Recent mammogram was clear. Any advice?