THE MELANOMA-SPECIFIC XMEL ANTIGEN IS EXPRESSED IN DYSPLASTIC NEVI

We have previously shown that a novel monoclonal antibody, XMEL, exhib ited reactivity with deep primary melanomas while showing no reactivit y with other tumours and normal tissue, XMEL was raised against a part of the extracellular domain of Xmrk, a growth factor receptor presume d to mediate melanoma formation in the Xiphophorus fish model. Here we investigate the range of XMEL immunohistochemical reactivity in paraf fin sections from human common acquired and dysplastic naevi of both j unctional and compound type, The strongest reactivity was observed wit h the compound dysplastic naevi. We conclude that the antigen recogniz ed by XMEL acts early in the cascade of genetic alterations underlying progression into malignant melanoma, Our results also support the not ion that the dysplastic naevus may play a role in progression of human malignant melanoma and may indeed represent the precursor stage.