For the last two months I have noticed a discolored area of skin about the size of a half dollar, adjoined to the areola of my left breast. There is no sensitivity, no lump. Two nights ago, I had pain in my armpit throughout the night, that was alleviated by sitting up. So, yesterday I got a mammagram and a sonogram and was given a clean bill of health. Not knowing what the discoloration is, I am still disconcerted. I have read several other posts regarding this similar occurance, but have read no explaination. Anyone know what causes this? I am 43, mother of 3 who just stopped breastfeeding an infant a year ago. Any thoughts on this would be appreciated.