Aesth. Plast. Surg. 17:335-338, 1993 Aesthetic _ Plastic Surgery @ 1993Springer-Verlag New York Inc. Local Reaction and Migration of Injected Silicone Gel: Experimental Study Cassio Menezes Raposo do Amaral, M.D., Vatdenize Tiziani, Maria Leticia Cintra, M.D., Ingrid Amstalden, M.D., and Fortunato Badan Palhares, M.D. Sho Paulo, Brazil Abstract. A study of the local and migratory effects of free silicone gel taken from a mammary prosthesis is reported. Thirty eight Wistar rats were injected in their subcutane- ous space with 1 cms of silicone gel. The animals were sacrificed on day: 3, 7, 15, 30, 60, 180, 240, 360, 420, 450. The visceral organs (heart, kidneys, lungs, stomach, gonads, liver, pancreas, spleen, intestine), as well as the tissue adjacent to the region of injection, were histologi- cally analyzed. There was no detectable silicone and no damage to the visceral organs based on routine histopatho- logical analysis. The greatest fibrosis was observed at the extremities of the disk formed by the silicone in the subcu- taneous space. Key words: Silicone--Silicone gel--Mammary prosthe- ses--Histopathological analysis--Experimental study Although there have been many articles published about the complications of the injection of silicone fluid [1-3, 5-8, 10, 11, 13, 18, 19, 22-24], research on local and systemic reactions to silicone gel is limited. Complications from the clinical use of in- jected silicone gel were described by Lewis [16], Kubota [15], and Megumi [17]. The permeability of the envelope, the "bleeding" of silicone gel mam- This research was developed at UNICAMP, State Univer- sity of Campinas, and at SOBRAPAR, Brazilian Society for Research and Craniofacial Rehabilitation Correspondence to Cassio Menezes Raposo do Amaral, M.D., Hospital de Cirurgia P14stica CrgmioFacial, Brazil- ian Society for Research and Assistance in Craniofacial Rehabilitation, SOBRAPAR, Av. Adolfo Lutz 100, P.O. Box 6028, 13081 Campinas, SP, Brazil mary prosthesis, and its tissue response have been documented by Raposo-do-Amaral et al. [21], Barker et al. [6], Hausner et al. [14], Vistnes et al. [25], and Cocke et al. [12]. Vistnes et al. [25] studied the local histologic reac- tion to silicone gel prostheses, ruptured and intact ones, which were implanted in the subcutaneous space of 30 rats. They were analyzed with the light optical microscopy on postoperative days 10 and 42. They observed that the fibrous capsule was thickest around the ruptured prosthesis. Surrounding the in- tact prosthesis an acute inflammatory reaction was seen on the tenth day. It showed polymorphonuclear leukocytes and round cells within the fibrous cap- sule. This reaction decreased and there was minimal cellular infiltration in the samples around the 42nd day. Vacuoles filled with gel were noted in the fi- brous capusle on the tenth day. Around the 42nd day the gel vacuoles became smaller and migrated throughout the connective tissue. In 1967, Rees et al. [22] observed silicone fluid in several visceral organs of animals injected on their peritoneal cavity with 7 cm 3of this material. In 1969, Boo-Chai [9] discussed the advantages of the in- jected silicone gel in augmentation mammaplasty as well as its complications. In 1991 Picha and Goldstein [20] studied the gel histocompatibility in animals during three months of followup. They found that the capsule stabilized by the 30th day, although the cellularity remained high. They also found that the amount of gel in the fibrous capsule at three months is less than that at one month and that the gel was more concentrated at the periphery of the fibrous capsule. The main purpose of this article is to present a long-time (450 days) histopathologic study of the local reaction and the possible migration of injected