The association of viruses with uveal melanoma

Electron microscopic examination of 57 ocular melanomas (54 human, two feline and one canine) revealed the presence of viral particles in six specimens. Herpesvirus particles were observed in one human specimen and were passed in human fibroblasts (WI-38), where they gave rise to intranuclear inclusions. A-type oncornavirus particles (oncogenic RNA virus) were observed in a second case, both in cells of tumor culture. In three human specimens and one feline specimen, togavirus particles were observed. Rubella is a member of this group, and the possibility that the presence of togavirus in these tumors is the result of latent ocular infection by rubella virus is raised. Herpes virus and RNA tumor viruses are widely considered as having a possible etiologic role for certain human cancers. The observation of togavirus is unexpected, as this virus has not been previously implicated in human or animal tumors. Injection of an RNA tumor virus (Gardner strain feline sarcoma virus) into the anterior chamber of newborn kittens resulted in the development of iris and ciliary body melanomas, many of which showed invasion and, in one instance, metastasis. This is the first animal model of a viral-induced uveal melanoma, and the histology and ultrastructure are described. These results emphasize the need for the continued investigation of the role of these viruses in uveal melanoma.