I don't quite understand that the areas cannot be biopsied. Certainly if they are seen, even on one view, they could be located and wire placement be done followed by biopsy but there may be informaton that you have not included.
I would never attempt to advise what you are asking but I would suggest that you seek another opinion regarding which type of surgery ... you don't state if you have seen an Oncologist yet and if not I think you should for that additional opinion about the surgery and treatment. Regards ...
I understand your concern, and my most immediate reaction was that I would have a mastectomy if I were you. But I am not you, and losing a breast at your age may be a big consideration against such an aggressive treatment.
My concern would be as yours in not knowing what those calcifications really are. I would also be concerned about having a lumpectomy/radiation treatment process in case you have a recurrence. Also, you may want to be at piece of mind that nothing is left in that breast that can act against you now or in the future. Last, with a mastectomy you won't need radiation.
These are just my thoughts, and not advice.
Please let us know what you decide, and maybe you could benefit also from a second opinion?
All the best, KAT