Diffuse iris melanoma: a report of 25 cases

Abstract

Background: Diffuse iris melanoma is a rare variant of iris melanoma that has a flat growth pattern and often presents as unilateral hyperchromic heterochromia and glaucoma. There have been no large clinical reports of diffuse iris melanoma.

Design: Single-center retrospective case series.

Participants: Twenty-five consecutive patients with diffuse iris melanoma.

Methods: A review of the clinical features, management, histopathologic analysis, and prognosis was performed.

Main outcome measures: Clinical features, histopathologic features, management, and prognosis.

Results: At the time of diagnosis, the mean patient age was 49 years. The initial complaint was unilateral darker eye color in 13 cases (52%) and blurred vision in 6 (24%). Six patients (24%) were symptom free. On presentation elsewhere, the initial diagnosis was iris melanoma or nevus in 11 cases (44%) and glaucoma in 14 (56%), 8 (32%) of whom had prior laser or surgical treatment for glaucoma. The 25 patients were observed for a mean of 30 months before the diagnosis of melanoma was suspected and referral to our center for evaluation. The mean intraocular pressure at referral was 36 mmHg, and the mean number of clock hours involved by tumor was 11. Heterochromia iridis was present in all 25 cases (100%), corectopia in 23 (92%), and ectropion iridis in 21 (84%). Associated findings included unilateral cataract in 8 (32%), a prominent episcleral (sentinel) vessel in 7 (28%), and anterior chamber inflammation in 5 (20%), and synechiae (anterior or posterior) in none. The tumor was managed by enucleation in 22 cases (88%) and by plaque brachytherapy in 3 (12%). Five cases (20%) were classified as spindle melanoma, 17 (68%) as mixed cell type, and 3 (12%) as epithelioid cell type. Therefore, histopathologic examination showed that 80% of cases contained epithelioid cells. All 22 enucleated cases were found to have tumor invasion in the trabecular meshwork. Tumor invasion of Schlemm's canal was found in 18 (82%), minor pars plicata in 12 (55%), and episclera in 7 cases (28%). Of seven cases with episcleral invasion, four underwent surgical treatment for glaucoma. Excluding one recent case, the patients were observed for a mean of 78 months. Liver metastasis developed in 3 cases (13%).

Conclusions: Diffuse iris melanoma is a serious ocular condition that causes unilateral hyperchromic heterochromia and secondary glaucoma, often leading to a delay in diagnosis. Local invasion of adjacent ocular structures is common, and distant metastasis occurs in 13% of cases at mean follow-up of 78 months.