Iris Melanoma in a Patient with Retinitis Pigmentosa.

This report describes the histopathological findings of an iris melanoma that developed in a patient with retinitis pigmentosa (RP). A 66-year-old man was referred to our hospital with a diagnosis of iris tumor. He had a medical history of RP for over 25 years. His best corrected visual acuity at presentation was 20/20 (OD) and 20/200 (OS). Slit lamp examination revealed an iris melanocytoma in his right eye and a brown iris mass involving the pupil in his left eye. Ocular fundus examination of his right eye showed diffuse chorioretinal atrophy with attenuated retinal vessels and scattered pigment. A diagnosis of iris melanoma was made and enucleation of his left eyeball was performed. Histopathological examination of the eyeball showed an iris tumor with proliferation of spindle cells positive for Melan-A, HMB-45, and S-100 protein by immunohistochemistry. Diffuse destruction of retinal architecture was observed, with loss of outer segment and replacement by glial cells. Accumulation of melanin pigment around retinal vessels was found in peripheral retina. These histopathological findings were compatible with advanced stage of RP. This case demonstrates that iris melanoma can occur in eye with RP.