Background: Ferry et al. (8) showed that 35 % of eyes which have been enucleated because of a clinically suspected malignant iris lesion did not reveal a histologically malignant iris tumor.

Methods: A 43-year old male presented with a blind, painful left eye, which has developed over a time period of 6 months. Ophthalmologic examination revealed the presence of pigmented iris stromal lesions associated with diffuse pigmentation of the chamber angle and the development of absolute glaucoma. A diffuse iridociliary malignant melanoma (ring melanoma) was suspected and the blind painful eye was enucleated. Histologic examination revealed the presence of a benign melanocytic lesion, i.e. a spindle cell nevus of the iris with surface plaques causing diffuse extension of the chamber angle, trabecular meshwork, Schlemm's canal, and the ciliary body.

Conclusions: The malignant potential of iris lesions may be difficult to assess on clinical grounds only. Histologically, benign melanocytic proliferation may cause diffuse extension into the ciliary body as well as the chamber angle leading to an increase in intraocular pressure. In order to reach a final diagnosis a biopsy of the lesion is necessary.