Dedifferentiation potential of iris melanomas.

A histopathological study was conducted on four cases in which a diffuse iris melanoma presented with glaucoma. Drainage surgery was performed on three eyes for medically non-responsive raised intraocular pressure, and all cases eventually (within 2-7 years) required enucleation for secondary glaucoma. In the iridectomy specimens the tumour melanocytes were small, uniform in size and spindle shaped, while in the enucleation specimens the tumour cells were epitheliod and pleomorphic. The dedifferentiated tumour in the enucleated eyes spread extensively within the anterior chamber and anterior uvea. In three cases there was evidence of intrascleral spread. However, none of the patients has died from metastatic disease in the follow-up period of 2-6 years since enucleation.