Have you already had a needle biopsy done? Atypical cells basically mean Abnormal cells (not cancer, but abnormal), and the surgeon needs to get a bit more of a tissue sample to be certain there are no bad cells around the same area. Try not to worry! The wire localization is done with mammography or ultrasound guidance. The Dr will find the area, numb you up, insert a needle to the area, insert a wire thru the needle, remove the needle, and you go up to surgery with a flexible wire which will guide the surgeon to the area that needs to be excised. When you wake up, you will have a small incision in the breast and may even go home the same day. You will be fine, and I hope all pathology results come out benign for you!
When they have to use the wire, that means it is too small to feel. Which in turn means early. He may mean that she/he is going to have the patholoigst look at it while you are in surgery to see if it is cancer.
I will pray for you.