A breast prosthesis may be formed by forming an outer layer on a mold, and filling the mold with a polymerizable foaming composition. The mold may be formed by forming a computer model of the prosthesis based on scanning a patient. The computer model may be used to form a solid model. A prosthesis may be coupled to the patient by coupling at least one metallic insert to the prosthesis and at least one magnet to the patient. Alternately, the prosthesis may be formed with a retaining harness integral to the prosthesis. In still another method, the prosthesis may be coupled to a retaining device surgically implanted in the patient.