U.S. patent application 20170367850 (applicant American Breast Care LP, Marietta, Ga.):
"In a method of making a breast prosthesis for use by a wearer having a body temperature, a plurality of dissolvable beads is placed into an open back of a breast-shaped mold. The open back of the mold is sealed. A suspension of an uncured silicone rubber liquid  and a plurality of phase change material pellets  is injected into the mold around the beads. The uncured silicone rubber is allowed to cure, thereby forming a breast shape. The phase change material has a latent heat of fusion at a melting point so as to remove heat from the wearer when the body temperature is at least at the melting point. The breast shape is removed from the mold and the dissolvable beads are dissolved from the breast shape."