Ultrastructural study of a corneal keloid.

A 69-year-old man developed keloid overgrowth on his left cornea in response to an injury from a fingernail. The lesion was removed by superficial lamellar keratectomy and was studied by electron microscopy, and light microscopy after immunoperoxidase staining for actin. The surgical specimen revealed disorganised, anteriorly atrophied and posteriorly vascularised connective tissue stroma. The epithelium was oedematous, thin, non-keratinised, and contained cells with features of myoblastic differentiation. Stromal fibroblasts were found in several distinct ultrastructural forms including young active fibroblasts, myofibroblasts, inactive fibroblasts (fibrocytes) and fibroblasts with prominently fibrillar cytoplasm. Fibroblasts with glycogen storage and/or pseudonuclear inclusions were also seen. Macrophages and lymphocytes were scattered in the stroma, and intact nerves were also present. An irregular 2-65 microns band of 10 nm filament meshwork existed at the posterior border of the keloid stroma, and deep localised patches of climatic degeneration were detected.