Immunohistochemical characterization of surgically removed subfoveal fibrovascular membranes.

Eighteen patients with age-related macular degeneration developed subfoveal membranes that were surgically removed and submitted for histopathological examination. Immunohistochemical techniques were performed, using a panel of monoclonal antibodies recognizing retinal pigment epithelial (RPE) cells, myofibroblasts, pericytes, endothelial cells, glial cells, smooth muscle cells and various types of macrophages. The PC10 antibody to proliferating cell nuclear antigen (PCNA) was applied as a marker of proliferating cells. The specimens displayed a core of neovascular stroma surrounded by a rim of more fibrous tissue. All specimens contained abundant RPE cells that in some cases appeared to envelop part of the membrane. Most cases had basal laminar deposits and thickened basement membrane material adjacent to the RPE cells suggestive of parts of Bruch's membrane. Often this Bruchlike membrane appeared at the surgical margin, forming a surgical cleavage plane. Chronic inflammatory cells were abundant, but polymorphonuclear leukocytes were notably absent. Nearly all specimens contained myofibroblasts and various types of macrophages. The presence of myofibroblasts suggests subretinal membrane contraction, which may induce new breaks and other pathology in RPE layer and Bruch's membrane.