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Editor,—Diffuse melanoma of the iris is an unusual variant of anterior uveal melanoma. It is usually characterised by diffuse, circumferential neoplastic involvement of the iris, chamber angle and, sometimes, ciliary body.1 2 Patients usually present with ipsilateral raised intraocular pressure and heterochromia. There is often a delay in both the diagnosis and treatment of these tumours owing to their atypical presentation.2 A tendency for ciliary body involvement and extraocular extension may account for their generally poor prognosis.
We present an unusual case with diffuse melanoma of the iris diagnosed by high frequency ultrasonography and fine needle aspiration biopsy.
A 79 year old man with unilateral glaucoma on the left eye developed pain, red eye, and heterochromia during his follow up. He had an ocular history of glaucoma surgery (Baerveldt implant) 1 year before presentation, and recent cataract surgery on the left eye.
Because of uncontrolled glaucoma, heterochromia, and diffuse yellow-white deposits throughout the anterior chamber, cornea, with vitreous cells on left eye, he was referred for ophthalmic oncology evaluation. The examination of right eye was found to be normal. On examination of the left eye, he was noted to have a best corrected visual acuity of 20/250 and intraocular pressures of 46 mm Hg. Slit lamp examination of the left eye revealed yellow-white keratic precipitates on the cornea and 4+ cells in the anterior chamber (Fig 1A and B). The iris was significant for clumps of similarly coloured debris and neovascularisation (Fig 1A and B). Ophthalmoscopy revealed vitreous cells and the retina appeared normal. A transillumination defect (3 × 3 mm) was observed between 5 and 6 o'clock inferiorly in the pars plana.
High frequency ultrasonography revealed deposits on the corneal endothelium, diffuse iris thickening, and a nodular thickening on the inferior quadrant of the ciliary body (Fig 1C). The diagnosis of the diffuse melanoma of iris was made by transcorneal fine needle biopsy of the anterior segment debris.
After a negative metastatic survey, the patient underwent enucleation with 50 Gy of postoperative radiation therapy. Histopathological evaluation of the enucleated eye confirmed the tumour to be a malignant melanoma with a diffuse involvement of the iris stroma (Fig 2A and B). Cytology revealed epithelioid malignant melanoma cells. Special stains of the harvested material was S100 positive (Fig 3A and B).
Diffuse melanoma of the iris is a rare entity among anterior uveal tumours.1 Classically, it is described as involvement of anterior uveal tissues in a complete ring, but it is used for any melanoma involving more than 6 clock hours of anterior uvea circumferentially.2 Jakobiec and associates reported that 13 of 183 (7%) patients with iris melanoma had diffuse melanoma; however, Jensen and associates reported 10 of 80 (12.5%) iris melanoma cases were diffuse melanoma.1 3
The ipsilateral glaucoma and heterochromia are the cardinal signs in this disease.4 The mechanism of glaucoma includes pigment dispersion, tumour invasion of the angle, angle closure, and iris and angle neovascularisation.4 The clinicians often pay more attention to the secondary glaucoma than to the heterochromia. So, there is usually a delay in diagnosis and often a history of previous glaucoma surgery in these patients.
Conventional B scan ultrasonography is not so helpful for anterior uveal tumours. Ultrasound biomicroscopy offers a better diagnostic method to evaluate the lesions of iris, chamber angle, and ciliary body.5 Transillumination is another useful test to assess the ciliary body involvement, although transillumination defects have been variably reported, ranging from 4% to 87% of patients with diffuse uveal melanoma.6 The other diagnostic tool is fine needle aspiration biopsy with an accuracy rate of 90% in diagnosis and a low risk of tumour seeding.4
Although our patient had a history of glaucoma and heterochromia, this case had an atypical presentation with diffuse tumour seeding in the anterior chamber and vitreous (a clinical picture similar to endophthalmitis). Clearly ultrasonographic biomicroscopy and fine needle aspiration biopsy were invaluable for the diagnosis and management of this case.
Enucleation is commonly performed for diffuse melanomas. But, despite surgery the prognosis for survival of these patients is typically worse than patients with nodular uveal melanomas of equivalent thickness. This may be due to the greater likelihood of epithelioid cells, a higher rate of extrascleral extension, and/or their delays in diagnosis.2 Our patient is still alive with no evidence of metastasis and recurrence after 1 year.