Synovial metaplasia of a periprosthetic breast capsule.

A 48-year-old woman presented for reconstruction mammoplasty 5 years after undergoing a mastectomy for breast carcinoma. She underwent tissue expansion, with subsequent placement of a permanent silicone implant, removal of the permanent implant because of asymmetry, and further tissue expansion for another attempt at permanent silicone implant placement. The periprosthetic breast capsule surrounding the initial permanent implant consisted of a lining intima, subintima, and fibrous capsule consistent with synovium on light microscopy, immunohistochemical studies, transmission electron microscopy, and scanning electron microscopy. Silicone was localized intracellularly within the lining cells and extracellularly within the fibrous capsule by electron probe microanalysis. We believe that this case represents synovial metaplasia of a periprosthetic breast capsule that was most likely induced by repeated manipulation and silicon exposure from silicone gel leakage and the prosthetic Silastic shell.