Given that Breast Cancer rates have nearly doubled since mammography became widespread (but deaths have remained about the same), one can assume that the extra cancers are mostly "in-situ", or encapsualted and unable grow.
So, a young lady has a positive on her mammogram. If the tumor is small, she has a 50-50 chance of the tumor being in-situ. Those are tough odds to play with. Personally, I would recomend against a needle biopsy, but instead get a lumpectomy from the best surgen in the business. Followed, of course, by aggressive nutritional therapy.