Capsular metaplastic changes described as "synovial metaplasia" have been reported in association with silicone gel breast prostheses. Initially this finding was thought to be more common with textured implants. Recent studies have shown no relation between implant shell type (textured vs. smooth). The incidence of this metaplasia has been shown to decrease with the age of the implant, suggesting that it is a transitional finding in capsular maturation. The metaplastic cells in the synovial metaplasia may have secretory characteristics, but the exact etiology and function of the metaplasia are not yet fully understood. Experimentally, a similar connective tissue reaction has been induced by repeated injections of air to produce the so-called "air pouch." The current study describes cartilaginous metaplasia in the capsule surrounding a silicone-filled, Cronin-type, Dacron-backed breast prosthesis. At 26 years after bilateral breast augmentation, this patient presented with breast pain and firmness. During surgical removal the implants were intact but the capsules were densely hyalinized, irregularly calcified, and on one side there was cartilaginous metaplasia within the connective tissue of the capsule. This had occurred independently of calcification. This was believed to be an unusual tissue response. Review of the English literature failed to identify a comparable case.
(C) 1999 Lippincott Williams & Wilkins, Inc.