Conservative biopsy excision and management of a large iris melanoma

Abstract

A 68-year-old man was referred with a right iris lesion, present for 10 years with noticeable growth over the last 24 months. Visual acuity (VA) was 6/6 bilaterally with normal intraocular pressures. A large inferonasal pigmented iris tumour was observed extending from 2:30 to 6 o'clock on the right iris ( Figure 1A). The lesion was raised, creamy coffee-coloured and associated with corectopia but not iris or angle neovascularisation ( Figure 1B). Gonioscopy showed the lesion adjacent to the angle but without visible encroachment of angle structures (dynamic gonioscopy), from approximately 3 to 5 o'clock ( Figure 1C). High-frequency ultrasound showed no macroscopic involvement of the ciliary body. Systemic review revealed no metastatic lesions and no history of systemic melanoma.Due to high suspicion of iris melanoma, surgical excision biopsy was performed, as the patient's preferred management, after careful discussion of options, including continued observation, localised external plaque radiotherapy, proton beam radiotherapy and laser photocoagulation. The major differential diagnosis of this iris lesion was an enlarging benign iris naevus.To minimise distortion and manipulation of the iris, with the potential to damage adjacent ocular structures and dispersion of tumour cells, an initial 'closed globe' approach was employed. Two small (1.2 mm), peripheral, temporal corneal paracenteses were made opposite the upper and lower margins of the lesion. The anterior chamber was filled with a large cushion of viscoelastic to elevate the iris away from the crystalline lens and to protect the corneal endothelium. The iris was incised radially from pupil to base via the paracenteses using microsurgical intraocular scissors and forceps. Thereafter, a large, stepped nasal corneal incision (145°) was made to enable excision of the tumour at the iris root. Five clock hours of the iris was removed without injury to lens, cornea or angle.Histology confirmed a malignant iris melanoma of mixed cell type, predominantly spindle B-cells with the tumour extending to the nasal excision margin. The latter was indicative of the potential of residual ocular tumour at the nasal margin. The lesion was further assessed and was focally positive for S100, diffusely positive for HMB45 but KI-67 negative. Fluorescence in situ hybridisation analysis confirmed