Expression of intermediate filaments in conjunctival melanocytic lesions.

BACKGROUND

To our knowledge there have been no studies on intermediate filament (IF) expression in conjunctival melanocytic tumors to date. Melanocytic lesions occurring at various body sites are known to express, in addition to the predominant IF protein vimentin, the epithelial-specific cytokeratins (CKs) and the neuronal IF peripherin. The present study was therefore carried out to assess the expression of IF proteins in conjunctival melanocytic lesions.

METHODS

Paraffin-embedded material from 34 tumors - 16 conjunctival nevi, nine specimens of primary acquired melanosis (PAM; eight with and one without atypia), and nine conjunctival melanomas - was assessed after the application of a panel of antibodies directed against diverse IF proteins, including vimentin, CKs and peripherin.

RESULTS

The most significant finding of this study was that all the tumors investigated expressed vimentin exclusively. While simple-epithelium CKs were found in epithelial cysts of nevi and in pseudoglandular portions adjacent to the melanoma, they were not identified in the tumor cells themselves. Similarly, peripherin and neurofilaments were not detected within any of the tumor cells.

CONCLUSION

The IF expression pattern of conjunctival melanocytic lesions differs from that seen in melanocytic tumors of other body sites (including uveal melanomas), in that it includes neither CKs nor peripherin.