A breast tissue expander is a temporary medical device used in the first stage of breast reconstruction following a mastectomy. It functions as an uninflated, balloon-like sac placed under the chest skin or muscle to gradually stretch the surrounding soft tissue. This stretching process creates the necessary space, or pocket, to hold a permanent breast implant or tissue flap later on. The expander is systematically filled over several weeks or months to slowly increase the volume of the breast mound. It is designed to be exchanged for a permanent prosthesis once the desired skin envelope size has been achieved.
The Physical Components of a Tissue Expander
The main body of a tissue expander resembles a deflated balloon and is constructed from a durable, flexible silicone elastomer shell. This shell is designed to be biocompatible and strong enough to withstand the internal pressure and stretching forces applied during expansion. The expander is surgically placed mostly empty, then progressively filled with sterile saline solution to facilitate gradual tissue growth.
A defining feature is the integrated injection port, which is the access point for the saline injections. This port is typically a small, firm structure made with a self-sealing membrane to prevent leakage after the needle is withdrawn. The port allows the practitioner to inject the saline through the skin and directly into the expander without additional surgery for each fill.
Many contemporary expanders include a small metallic component, such as a magnet, in the port to aid in locating the site. A magnetic finder held outside the skin guides the practitioner precisely to the center of the integrated port. This port usually feels like a small, hard bump located under the skin. Some expanders also feature suture tabs, which are small extensions used to fix the device to the chest wall and prevent unwanted rotation.
Variations in Expander Design
Tissue expanders come in various designs, primarily differing in shape and surface texture. The surface of the silicone shell can be either smooth or textured, which affects how the expander interacts with the surrounding tissue. Textured surfaces were historically favored because they promoted tissue ingrowth, reducing the risk of malposition and capsular contracture.
Due to concerns surrounding textured devices, the current trend is shifting toward the use of smooth-surface expanders. While smooth devices may carry a slightly higher risk of rotation, they are considered a safer alternative by many surgeons today. Manufacturers have addressed the rotation issue by incorporating suture tabs into smooth devices for secure fixation to the chest wall.
Regarding shape, models are broadly categorized as round or anatomical (teardrop-shaped). Round expanders provide uniform projection and volume and are less likely to rotate. Anatomical expanders are designed to mimic the natural slope of a breast, concentrating greater volume in the lower half for a more natural profile. These anatomical devices are usually designed with textured surfaces to maintain their specific orientation and prevent rotation, though smooth versions are becoming more common.
Appearance During the Expansion Phase
Immediately following surgery, the chest area may appear flat, bruised, and swollen. The expander is only partially filled upon placement to avoid undue tension on the healing mastectomy skin flaps. As the weekly or bi-weekly saline injections begin, the chest gradually develops a noticeable mound.
The skin over the expander will become increasingly stretched and may appear taut or shiny as the volume increases. Because the expander is designed to create a large pocket of tissue, the resulting shape is typically firm and high on the chest wall. This temporary shape often looks somewhat unnatural, sometimes having a “shelf-like” appearance rather than the soft, natural slope of a final breast.
Patients may be able to feel or see the outline of the injection port, particularly when the skin is thin or the expander is fully inflated. This visible bump is normal and confirms the location of the access point for filling. This high-riding, firm appearance is temporary, and the final, softer, and more naturally shaped breast is achieved only after the expander is removed and replaced with a permanent implant or tissue reconstruction.