Phakomatous choristoma (Zimmerman's tumor). Immunohistochemical confirmation of lens-specific proteins.

BACKGROUND

Phakomatous choristoma is a rare, congenital, ocular adnexal tumor that is presumed to be of lenticular anlage based on light and electron microscopy.

METHODS

The authors performed immunohistochemistry using standard commercially available antibodies against vimentin, S-100 protein, and several cytokeratins on a phakomatous choristoma that was excised from the right lower eyelid of a 10-week-old white boy. In addition, a battery of antibodies against lens-specific proteins, including alpha, beta, and gamma crystallins, was used.

RESULTS

The tumor cells showed intense immunoreactivity for all lens-specific proteins tested. The epithelial cells of the phakomatous choristoma stained positively for S-100 protein and vimentin, the intermediate filament normally found in lens epithelial cells. Keratin markers were negative.

CONCLUSIONS

The results of immunohistochemistry indicate that the cells of phakomatous choristoma synthesize several types of lens-specific proteins. Complementing previous light and electron microscopic studies, these data strongly support Zimmerman's conclusion that this pediatric adnexal tumor is a choristoma of lenticular anlage.