It’s hard to accept in 2020 but all scans have limitations and frustrating as it is not everything shows up. After MRI not showing my 86mm of DCIS (after two small invasive tumours removed) I whipped the whole breast off and wished so much that I had opted for immediate mastectomy in the first place and not fiddled around with wires and wide excisions and scans that failed to show the extent of disease. It is my only regret. Now I have both off.
It’s a difficult time for you, and you just would be feeling so out of control with it all. I feel for you and hope you get good advice and treatment. Your life is more precious than your breast.