Immunoreactivity for latent membrane protein 1 of Epstein-Barr virus in nevi and melanomas is not related to the viral infection

Epstein-Barr virus (EBV) is a human herpes virus with oncogenic potential, associated with several malignancies. The EBV-encoded latent membrane protein 1 (LMP1) is one of nine proteins regularly expressed in virally infected and immortalised B lymphocytes. We now document the consistent immunoreactivity for LMP1 in 90% of 65 nevi and melanomas, using the monoclonal antibody cocktail CS1-4. The immunocytochemical findings, however, were not confirmed using reverse-transcription polymerase chain reaction (RT-PCR) experiments, which failed to demonstrate any actual expression of LMP1 mRNA. In situ hybridisation for EBV-encoded RNAs (EBERs 1 and 2) and PCR amplification of EBV genomic sequences also failed to document any viral infection. Several normal and neoplastic human tissues have also been immunostained for LMP1, without any positive staining, with the exception of a minor percentage of skin melanocytes and of normal blasts of the myeloid and erythroid lineages. We conclude that the vast majority of nevi and melanomas express a still uncharacterised molecule, cross-reacting with anti-LMP1 (CS1-4) antibodies, which may be considered a consistent marker of melanocytic proliferations. The immunoreactivity of normal and neoplastic human tissues for the anti-LMP1 reagent should not be taken as evidence of EBV infection.