[Synovial metaplasia around breast implants].

Three cases of the periprosthetic breast capsules showing typical features of synovial metaplasia are presented. The histological picture is characterized by the presence of cellular layer mimicking synovial membrane. These elements are devoid of basement membrane, otherwise, nevertheless, they strongly resemble single- or multilayered epithelium. Focally, the differentiation towards giant multinucleated cells is noted. Immunohistochemical profile, as well as the ultrastructure of the cells, confirms their histiocytic origin with advanced differentiation towards elements of the synovial membrane. These histological features are referred to as synovial or synovial-like metaplasia. They are found in considerable fraction of textured breast implant capsules. The pathogenesis remains uncertain; however, similar picture was observed in other locations in association with prolonged or repeated action of mechanical forces. Thus, movement of the implant in situ is the most probable trigger of synovial metaplasia.