• Written By: Patricia Chévez-Barrios, MD
    Ocular Pathology/Oncology

    The authors conducted this study to establish diagnostically useful immunohistochemical profiles for distinguishing among retrocorneal membranes of different sources, with particular attention paid to collagenous membranes.

    They reviewed clinical files for penetrating keratoplasty and Descemet stripping endothelial keratoplasty (DSEK) corneal specimens. They subsequently performed immunohistochemical staining on five enucleated control globes, 32 penetrating keratoplasty specimens and six DSEK specimens to analyze normal corneal epithelium, stroma and endothelium; stromal scars; endothelial abnormalities; and retrocorneal membranes. Paraffin sections were stained with hematoxylin and eosin, periodic acid-Schiff and Masson trichrome methods. They performed immunohistochemical analyses with commonly available monoclonal and polyclonal antibodies for various cytokeratins (CKs), CD34, alpha-smooth muscle actin (SMA) and vimentin.

    Five subtypes among 28 retrocorneal membranes were characterized. Twelve fibrous (keratocytic) membranes of stromal origin had coarse collagen and immunostained negatively for all CKs but strongly for vimentin and alpha-SMA, the last the only marker of diagnostic value. Nine metaplastic endothelium-derived membranes produced delicate collagenous matrices and immunoreacted with CK7, vimentin and alpha-SMA. Two epithelial multilaminar or monolaminar membranes reacted with CK cocktail and wide-spectrum CK, mildly with CK7 (not observed in orthotopic surface epithelium) and negatively for alpha-SMA and vimentin. The final two categories were indeterminate or nonimmunoreactive (three specimens) and mixed (two specimens).

    The authors conclude that immunohistochemistry provides a valuable supplemental approach for determining the composition of retrocorneal membranes. Clinical correlations established that these membranes develop after serious inflammatory disorders, prolonged wounding or ulcerations, and multiple surgeries (an average of 3.4 per patient). The authors provide the following immunopatterns as a diagnostic aid: (1) the most common stromal (keratocytic) fibroblastic membranes are strongly α-SMA and vimentin positive and negative for all types of CK; (2) metaplastic endothelial membranes are CK positive (especially CK 7), vimentin positive and mildly to moderately α-SMA positive; and (3) membranes of epithelial downgrowth are strongly CK cocktail positive, mildly to moderately CK 7 positive and α-SMA and vimentin negative. A paucicellular admixture of persisting metaplastic endothelial cells can be encountered in predominantly keratocytic and epithelial membranes.