I don't know ANYTHING about mastectomies. I'm a guy, and mercifully, no one in my family has suffered from breast cancer. But, if they removed the tissue inside the breast while leaving the skin and nipple, couldn't they simply put a silicone or saline implant directly into the now-empty bag? Sorry for sounding a bit crude, but it seems to me that it wouldn't be much different from any other young woman getting implants.
sw