It has never been scientifically proven that silicone breast implants cause breast cancer, rheumatism or immunity disorders. It is true that the prostheses used to be filled with a liquid silicone gel. If there is a tear in the implant's shell then the gel could leak out and spread into the body. Fortunately this was in the past!Modern silicone implants have a strong silicone wall and are filled with a firm silicone mass. If there is a tear in the wall the solid gel doesn't leak into the body.