Epithelial downgrowth. Report of 2 cases diagnosed by ocular biopsy.

Epithelial downgrowth is an uncommon complication of ocular surgery or adverse consequence of accidental trauma, caused by surface squamous epithelium that has gained access to the inner compartments of the eye. Once embedded in the eye, squamous epithelium spreads over contiguous structures, interfering with normal aqueous outflow and vision. The pursuit of improved therapies is ongoing, but the greatest chance of preventing blindness is with early recognition. Two cases of epithelial downgrowth diagnosed from a corneal button and an iris biopsy are presented to familiarize pathologists with this disorder. In the appropriate clinical setting, the presence of stratified squamous epithelium, with or without goblet cells, is diagnostic of epithelial downgrowth. Other than congenital epithelial inclusion cyst (choristoma), stratified squamous epithelium is not found inside the eye. Surface epithelium introduced surgically or traumatically needs to be differentiated histologically from ectopic corneal endothelium and metastatic carcinoma.