Patients who have had a mastectomy for breast cancer may require tissue expansion prior to breast implants. Tissue expansion refers to a process where a plastic device filled with saline is inserted partially under the chest (pectoral) muscle at the time of a mastectomy or breast cancer removal surgery. Then, in the office over a  few months, the device is gradually filled with saline fluid to increase the size of the breast thereby stretching the skin. Once the skin has been stretched to the desired size, at a separate surgery the tissue expander is removed and replaced with a breast implant (either saline or silicone). This is a good way to help restore breast symmetry in women who have had a complete or partial mastectomy due to breast cancer or trauma.