A 45-year-old white man had chronic ulcerative keratitis, believed to be herpetic, for two years. Penetrating keratoplasty was performed after a descemetocele had almost perforated the cornea. Microscopically, epithelial cells at the edges of the ulcer contained reddish-purple intranuclear inclusions consistent with Cowdry type A inclusion bodies, although they were not surrounded by a halo. Electron microscopic studies of the formalin-fixed, paraffin-embedded tissue revealed intranuclear, cytoplasmic, and extracellular viral particles that were morphologically typical of herpes simplex.
A brief review of the literature establishes the practical application of electron microscopy as a diagnostic tool, especially when inclusion bodies suspected of viral origin are observed in tissues that have been stored in formalin or embedded in paraffin, even for a prolonged period of time.
Font RL. Chronic Ulcerative Keratitis Caused by Herpes Simplex VirusElectron Microscopic Confirmation in Paraffin-Embedded Tissue. Arch Ophthalmol. 1973;90(5):382-385. doi:10.1001/archopht.1973.01000050384010