Silicone gel-filled breast and testicular implant capsules: a histologic and immunophenotypic study.

The immunophenotypic characteristics of silicone gel-filled breast and testicular implant capsules have not been well described. Therefore, we studied 17 paraffin-embedded tissue sections from 9 breast implant patients and 1 testicular implant patient to assess the type and extent of inflammatory responses present. Immunohistochemical analyses were performed on paraffin-embedded tissue sections for expression of CD20, CD45RO, betaF1, CD68, CD44, kappa and A immunoglobulin light chains, and bcl-XL (a member of the bcl-2 family of proteins involved in apoptosis). The most common histologic features included prominent T-cell and foamy macrophage reactions with foreign body giant cells and granulomas in a dense fibrovascular connective tissue. Foci of polyclonal plasma cells and acute inflammatory cells were variably present. In one case, there was reactive germinal center formation, a novel finding. A "pseudosynovium" at the implant capsule interface was present in the majority of cases as previously described; it showed reactivity with CD68. Thin strands of highly refractile, nonpolarizable material, consistent with silicone, were regularly noted in intra- and extracellular locations. The immunohistochemical results included reactivity of the majority of lymphocytes with CD45RO and/or betaF1 (confirming an anamnestic reactive T-cell phenotype), and reactivity of the macrophages, giant cells, and "pseudosynovium" with the macrophage/histiocyte marker, CD68. The reactive germinal centers were positive for CD20. Reactivity for CD44, an activation and intracellular adhesion marker, was frequently observed in the foamy macrophages and foreign body giant cells and has not been previously reported. The plasma cells demonstrated polyclonal immunoglobulin light-chain reactivity, consistent with a reactive process. These findings suggest that silicone implants induce chronic inflammatory responses in many adjacent capsules, which consist of anamnestically responding T cells, reactive B-lymphocytes, and macrophages.