Your surgeon should be able to do a needle biopsy. That way they can find out what you're dealing with and not worry about taking it out at this point. It can be done under ultrasonic guidance in most cases so that you don't have to worry about radiation from mammograms to localize the lesion. They locate the mass on u/s, then use a thin needle with a little "clamp" on the end to take a sample of tissue out of it for analysis.
Please do get it biopsied soon, though. Malignant breast CA's that are estrogen dependent grow like wildfire during pregnancy. Don't put it off. Your babies need you alive more than they need your breasts.
(I'm a mammographer-I've seen it happen)
If it makes you feel any better, I had a sizable fibroadenoma removed about 10 years ago, with an incision that spans about 1/3 of my areola. My milk supply is slightly lower on that side, but not enough to make a difference in anything. A good surgeon can spare most of your ducts in a simple bx.
My prayers are with you.