You say this white mark has been there for quite some time and now on the nipple too.
Do you think it is spreading?? is the skin there normal?? If there is no discharge and no pain and the skin is normal then it could be vitiligo
. Of course to confirm one ha to examine it. I would suggest you visit your local dermatologist
so the appropriate treatment can be started.
Also check if there are any lumps in the breast associated with the swelling.
Please feel to mail me for any further queries and sorry for being vague, but you need to be examined to be able to give a proper diagnosis, since i havent seen the lesion.
Thank you for your query