What cup size would a 250cc implant produce after a mastectomy?

I think the best way to answer this question is to explain how cup size is determined.  The cup size is a ratio of the chest circumference to the size of the breast.  So a smaller implant would produce a larger cup size on a very petite woman than a large-chested woman.  Having said all that, a 250 cc implant would be a very small cup size on even a petite woman.  To better answer this question, pics of your body frame and/or height weight would be helpful, but having done hundreds of breast reconstructions, I can say that even on the most petite women, I don't think I have ever gone so small as a 250cc implant, which would provide at best an A cup on a small woman.  You might wish to consider doing tissue expanders first so that you have complete adjustability with your implant size prior to placing the final implants.  Best of luck with your reconstruction!

will produce a very small mound and even smaller if you have a wider band size.  If you're having an expander placed, you can see what your size will be at different fill volumes.  If you're having an immediate reconstruction with implant, most surgeons have sizers that you can use to help visualize what you could be like afterwards.