An antimelanoma monoclonal antibody and the histopathology of uveal melanomas.

Monoclonal antibody ME491 identifies a cutaneous melanoma-associated antigen in formaldehyde-fixed, paraffin-embedded tissues. This antibody was applied to tissue sections from 79 cases of formaldehyde-fixed, paraffin-embedded uveal melanomas. Sixty-nine (87.3%) of the 79 cases showed staining by monoclonal antibody ME491, thus demonstrating an antigen shared by cutaneous and uveal melanomas. No relationship between the staining pattern and the patient outcome was detected. Twelve (85.7%) of the 14 cases in which balloon cells were present stained with the antibody. The antibody stained the long posterior ciliary nerve in 12 (38.7%) of 31 cases in which the nerve was present in tissue sections. The antibody cross reacted with the retinal pigment epithelium (16.5% of cases) and a variety of normal nonocular tissues.