The differential diagnosis of malignant melanoma of the iris. A clinical study of 200 patients.

The records of 200 consecutive patients referred to the Ocular Oncology Service of Wills Eye Hospital because of an iris lesion suspected of being an iris melanoma were reviewed. On clinical evaluation, 24% of the lesions met the criteria for the diagnosis of iris melanoma and 76% were diagnosed as simulating lesions (pseudomelanomas). The most common pseudomelanomas included primary iris cyst (38%), iris nevus (31%), essential iris atrophy (5.7%), iris foreign body (4.5%), peripheral anterior synechia (2.5%), and iris metastasis (2.5%). Less frequently encountered pseudomelanomas included aphakic iris cysts, leiomyoma, melanocytoma, reactive lymphoid hyperplasia, adenoma of iris pigment epithelium, iridoschisis, and other miscellaneous entities. The clinical features that are helpful in differentiating the more common iris pseudomelanomas from true melanomas are discussed. Correct clinical identification of these simulating lesions may prevent unnecessary surgery or other treatment.