Retinoinvasive malignant melanoma of the uvea.

AIMS: To define a retinoinvasive phenotype of uveal melanoma based on an informative case and survey of literature.
METHODS: A 65-year-old woman developed a circumscribed mixed cell type melanoma of the ciliary body that was locally excised. After 6 years, secondary glaucoma evolved. Three years later a ring melanoma was diagnosed and the eye was enucleated. The histopathological material was analysed by immunohistochemistry.
RESULTS: A spindle cell type ring melanoma infiltrated the iris and ciliary body diffusely, and extended through the aqueous outflow channels and iridocyclectomy flap extrasclerally. The choroid was uninvolved. Instead, tumour cells spread to the vitreous and along the ciliary epithelium, adhered to the hyaloid face and retinal surface, and extensively invaded the neuroretina, the retrobulbar optic nerve, and perineural space. They were labelled for S-100 protein, vimentin, and in the neuroretina for cytokeratins 8 and 18. No evidence of systemic disease is evident 5 years after enucleation. Three identical tumours of the iris and ciliary body that extensively infiltrated the neuroretina and retrobulbar optic nerve were identified from previous literature.
CONCLUSION: Retinoinvasive melanoma is a rare but distinct phenotype of uveal melanoma, different from circumscribed and most diffuse melanomas that may erode the overlying retina and infiltrate the optic nerve that do not invade non-adjacent retina. Retinoinvasive tumours tend to evolve from a ring melanoma and they grow slowly, which may favour emergence of tumour clones able to migrate, adhere to, and invade into the neuroretina, analogous to the metastatic cascade. Frequent secondary angle closure glaucoma may promote invasion into the optic nerve.