RESUMO
During the past two decades, silicone (polydimethylsiloxane) has become one of the most extensively applied biomaterials. Although pure silicone is relatively inert and usually causes only minimal tissue reactions, it has been reported to evoke a definite foreign body reaction. We studied five cases of silicone-induced granulomas in various sites; two in the breast, one in the breast and axillary lymph nodes, one in the subcutis of the abdomen, back and extremities and one in the eyeball, to illustrate the salient histopathologic features of reactions to silicone with particular emphasis to its differences from paraffin granuloma. For this, 17 paraffinomas were also studied. Tissue reaction to silicone liquid and gel was characterized by numerous round to oval empty cystic vacuoles, mild to moderate fat necrosis, foreign body reaction, a variable degree of mononuclear inflammatory cell infiltration and mild focal fibrosis. The cystic spaces were relatively uniform and showed a snow-man like appearance. In contrast to the silicone granulomas, the paraffinomas, also refered to as sclerosing lipogranulomas showed diffuse sclerosis and frequent calcification around the cystic vacuoles. The cystic spaces in paraffinomas were swiss cheese-like configuration, and the content of the cystic spaces was dirty and frequently calcified. However, there were certain similarities between these two types of granulomas particularly in the early phases of the reaction, therefore, the history of silicone injection or implant, is sometimes critical to the diagnosis of silicone granuloma. Despite great technologic advances in the manufacturing of prostheses and medical equipment, droplets and/or particles of silicone still escape into the body tissues in a variety of ways; therefores, the pathologist should always wonder whether the histologic reaction observed is due to silicone or to some other foreign material including paraffin.