Myxomatous corneal degeneration: a clinicopathological study of six cases and a review of the literature.

Thirteen cases with myxomatous changes of the corneal stroma have been reported to date. We report six additional cases with clinical, histopathological, and immunohistochemical data. The clinical appearance is most often a gelatinous, whitish elevation with insidious onset. Histopathologically, there are inconspicuous spindle- and stellate-shaped cells in a loose, myxoid matrix. The typical location is in the anterior cornea beneath the epithelium, with varying degrees of extension into the stroma. Vimentin and smooth-muscle actin immunohistochemical stains are characteristically positive, and staining occasionally may be seen with muscle-specific actin, whereas CD34 staining usually is negative. In most cases, myxomatous changes are a degenerative process involving transformation of stromal keratocytes into cells with prominent secretory activity and myofibroblastic differentiation. Most occur in corneas with a history of ocular disease or trauma that disrupts Bowman's layer. We suggest labelling lesions with these features as "myxomatous corneal degeneration." So-called "primary corneal myxomas" also exist where there is no significant history. It remains unclear whether the myxomatous changes in such lesions are neoplastic or degenerative. Myxomatous corneal changes are likely under-recognized and under-diagnosed.