Illustration shows a tissue expander placed below the chest muscle as part of breast reconstruction with an implant.

A breast implant that's placed below the chest muscle is called a subpectoral breast implant. It's often done in two operations. First, a plastic surgeon places a balloonlike tissue expander below the muscle. Over a period of a few weeks to months, a healthcare professional may slowly fill the expander with saline to the size you prefer. In a second operation, a plastic surgeon removes the expander and replaces it with a breast implant.