A breast tissue expander (T.E.) is a temporary, balloon-like medical device used in the first stage of breast reconstruction following a mastectomy. Its purpose is to gradually stretch the chest skin and muscle tissue to create a pocket large enough for a permanent breast implant. The expander acts as a placeholder, allowing the body to slowly generate the necessary space and skin envelope over weeks or months. This process is a common method for patients choosing implant-based breast reconstruction.
Physical Anatomy and Materials
The expander itself is a flexible, empty sac, similar to a deflated balloon, made from a durable, medical-grade silicone elastomer shell. This shell provides a biocompatible and tough outer casing designed to withstand the stretching forces as the device is inflated over time. When initially implanted, the expander is relatively flat or only minimally inflated to establish its position within the chest wall.
The surface of the outer shell can be either smooth or textured. Historically, textured surfaces were common, but many surgeons now prefer smooth expanders due to recent safety concerns. The flexible nature of the silicone shell allows it to be surgically placed in a collapsed state and gradually stretched. The material is thicker and firmer than the shell of a permanent breast implant because it must endure the repeated expansion process.
Variations in Shape and Profile
Tissue expanders come in different shapes to help surgeons create a pocket that will best suit the final permanent implant and the desired breast contour. The two main shapes are round and anatomical, often called teardrop. A round expander has a circular base with a uniform projection across its surface, creating a more spherical final shape.
An anatomical or teardrop-shaped expander is designed with a sloped profile, meaning it is narrower at the top and fuller toward the bottom. This shape better mimics the natural silhouette of a breast, which has less volume in the upper pole. Surgeons also choose expanders based on their profile, which is the height or distance the device projects outward from the chest wall. Profiles range from low and moderate to high, directly influencing the final projection of the reconstructed breast mound.
The Filling Mechanism
The tissue expander includes a self-sealing injection port, which allows for the gradual inflation of the device after surgery. This port is a small, firm component that is either integrated into the expander’s surface or connected to it by a short tube and positioned remotely beneath the skin. The port contains a reinforced metal backing plate or is designed to be magnetic, which aids the clinician in locating it accurately beneath the skin.
During office visits, a specialized, fine needle is used to puncture the skin and the port’s self-sealing membrane. A sterile saline solution is then injected into the expander to incrementally increase its volume. The one-way valve within the port ensures the saline solution remains inside and prevents leakage between filling appointments. This controlled filling process is repeated until the surrounding tissue has stretched to the desired size and shape.
Placement and Visualization
Once surgically placed, the expander is positioned beneath the chest muscle (subpectoral) or on top of the muscle (prepectoral), depending on the patient’s anatomy and the surgeon’s plan. Immediately after surgery, the chest area may appear relatively flat or only slightly mounded because the expander is only partially filled. As the expansion process begins, the visible changes are gradual, with the skin slowly stretching over the increasing volume of the device.
During the initial phases of expansion, the shape of the breast mound may look temporarily unnatural, often appearing higher or more projected than a natural breast. It is common to feel the firm edges of the expander or the small, hard area of the injection port beneath the skin, especially before the final volume is achieved. The entire expanded structure is temporary, serving only to create the necessary tissue pocket until the permanent, softer implant is exchanged for the expander in a subsequent procedure.