there's a website from the American Society of Plastic Surgeons that completely breaks down all of those codes, and they have a CPT corner in every issue of their magazine. You should see if your physician subscribes to that magazine.
According to the archived files, it says that that when a tissue expander is removed and replaced w/ a permanent prosthesis, report 11970 if no other procedures are performed. This code includes exposure, incision of the capsule to access the expander, removal of the expander and the injection port, and placement of a permanent prosthesis. Coding for separately for any of these components is unbundling.
Good luck!