Taken OUT in Round 1

SO the pathology and radiology results post surgery resulted in a very discouraged phone call from my doctor with a very somber tone and news of "Not good at all. Very bad. Invasive. Mastectomy, PET scan, MRI. I am sorry to deliver such terrible news. Didn't see this coming at all. Didn't show on mammogram."  I know there were other words in there, but I didn't hear them really.  I think I heard "we were prepared about taking larger margins, right?"  Well yeah. I was prepared for that, but mastectomy?  I guess I knew it could happen but I wasn't really prepared for it.
So my mind has been reeling.  If they didn't see anything in the left breast mammogram that led them to think this was more serious, what didn't they see on the right?  Do I need to have it all removed? I am so confused.
I was not at all prepared to hear "it's worse than we thought."  I wasn't.  I just wasn't. I was prepared for maybe some larger margins and taking a little more, but mastectomy? I just wasn't prepared. So I guess I am down for the count. I really didn't expect to go out in the first round.