Epibulbar fibroma of the conjunctival substantia propria.

A 39-year-old black woman had a 12-year history of slowly progressive left temporal juxtalimbal conjunctival swelling. The lesion was freely movable over the surface of the globe and was believed to be situated within the substantia propria. Histopathologic evaluation of the excised tissue disclosed that it was a collagenous mass of lamellar architecture, with a hypocellular dispersion of mesenchymal cells and a scattering of capillaries in the absence of inflammation. Electron microscopic examination revealed that the lamellar arrangement had regular lobular subdivisions composed of collagen fibers approximately 50 nm in diameter. Compressed fibroblasts occupied the peripheries of the lobules; the former exhibited abundant rough-surfaced endoplasmic reticulum and failed to elaborate basement membrane material. Delicate processes of the fibroblasts extended into the centers of the collagenous aggregates. To our knowledge, this is the first convincingly documented case of an acquired fibroma of the substantia propria of the epibulbar conjunctiva. The differential diagnosis in this case included related fibroblastic and simulating nonfibroblastic lesions.