@Rubylulu Aw, so sorry to hear about your situation. It is really frustrating when they didn’t detect the DCIS in earlier scans. I hope it works out for you.
For me, I have no choice but hope they got it all. There is no more appreciable breast tissue to take out and my breast surgeon said if he takes more under the skin, it may result in flap necrosis. He did say if I insisted (against his advice), he could cut out a skin eclipse at the area of the margin and it will result in a big scar and they will probably not find anything.
It sucks that we go through mastectomy to be in the clear, but still have to monitor for residual disease.