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Pigmented iris lesion documented in an asymptomatic patient
Slit lamp exam of the ocular adnexa and anterior segment of the right eye showed a homogeneous iris mass.
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A 70-year-old white woman was referred to the New England Eye Center for evaluation. The patient noted seeing a “spot” on her right eye for more than 10 years. She denied decreased vision, pain or redness. She was unsure if the “spot” had grown in size over the past 10 years.
The patient’s review of systems was unremarkable. Her ocular history was significant for bilateral nuclear sclerotic cataracts and an iris lesion identified at an outside facility. She stated that she was healthy and was not currently taking any prescription medications or eye drops. The patient denied smoking or alcohol intake.
Examination
| Isabel Balderas | Tom Hsu, MD |
On examination, the patient’s best corrected visual acuity was 20/30 in both eyes with a slight hyperopic correction. IOP, extraocular motility and pupillary examination were normal in both eyes. There was no afferent pupillary defect in either eye.
Slit lamp examination of the ocular adnexa and anterior segment of the right eye revealed a homogeneous iris mass spanning the 5:30 to 8 o’clock positions (Figure). There was mild corectopia of the pupillary margin. The mass measured 4.3 mm from pupil margin to anterior chamber angle and 6.3 mm in its longest dimension. There was no pigment dispersion, neovascularization, satellite lesions, ectropion uveae or sectoral cataract. Gonioscopy of the right eye indicated the lesion approached the posterior trabecular meshwork; however, the angle was open without angle seeding. Ultrasound biomicroscopy showed a homogeneous mass indistinguishable from adjacent iris tissue, measuring approximately 1 mm in the anterior-posterior dimension. The mass did not extend into the angle or ciliary body.
Slit lamp examination of the left eye was unremarkable. Dilated fundus examination of both eyes was unremarkable.
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Image: Chaturvedi V, Duker JS |
What is your diagnosis?
Pigmented iris lesion
These findings in a 70-year-old woman without ocular complaints are most consistent with an iris cyst, nevus, metastasis or melanoma.
Differential diagnosis
The most important entity to rule out in a suspicious iris lesion is melanoma. To clinically diagnose an iris melanoma, the lesion must possess some of the following features: locally replace normal iris stroma, be at least 3 mm in greatest diameter or 1 mm in thickness, or display prominent vascularity, ectropion of the iris, sectoral cataract, secondary glaucoma or photographic documentation of growth.
Options available to the patient include observation, biopsy, local resection (eg, sector iridectomy), radiation therapy and enucleation. After discussing these options with the patient, it was decided to observe the patient. Upon follow-up 8 months later, the mass was found to have grown on ultrasound biomicroscopy from 1 mm to 2 mm (anterior-posterior dimension). Grossly, there was no change in the other dimensions of the lesion. Furthermore, the mass now involved the iris angle. There was no pigment dispersion, ectropion, increased vascularity, iris or angle seeding, or elevated IOP. The patient continued to deny any visual complaints.
At this time, the iris mass appeared to be actively growing, yet producing no ocular symptoms. These findings were most consistent with an iris melanoma.
Discussion
Iris melanomas are a rare form of ocular melanoma, representing only 5% of all uveal melanomas. They typically affect middle-aged white patients, typically with lighter-colored irides (eg, blue).
The clinical features of biopsy-proven iris melanomas have been well documented. On average, they are 6 mm in largest diameter and 2 mm thick. A majority of the lesions occur on the inferior half of the iris. Almost half are associated with corectopia, ectropion and prominent vascularity. About one-third of patients will have elevated IOP and/or pigment dispersion. Iris melanomas grow slowly and will locally invade adjacent structures such as the angle or ciliary body.
Iris melanomas are thought to arise secondary to sun exposure. This could also explain why the inferior half of the iris is more commonly involved than the less-sun-exposed superior half. Spindle B is the most common cell type found in iris melanomas, followed by mixed and epithelioid cell type.
The metastatic rate of biopsy-proven iris melanoma is roughly 5%. The most common site of metastasis is the liver. Given this low percentage, it is important to recognize features indicative of metastasis. The most predictive features include advanced age at diagnosis, IOP greater than 22 mm Hg, vision less than 20/20, extraocular extension, involvement of the angle or iris root, epithelioid pathology and surgical manipulation of the lesion before referral.
Management
Management of iris melanomas requires an understanding of all options available given the clinical picture. If there are limited clock hours involved (less than two) and there is no evidence of growth or seeding, observation may typically be employed. However, local resection is indicated if there is documented, significant growth, decreased vision or increased IOP. Enucleation is reserved for patients with extensive lesions, while radiation is an option for patients with extensive lesions who are unable to undergo a surgical procedure. Biopsy of suspicious iris lesions typically is reserved for cases in which the practitioner is unsure whether to resect the lesion.
Combining our understanding of the behavior of iris melanomas, the nature of this patient’s iris melanoma and then providing her with all management options, she ultimately decided to continue with observation. Six years since her initial visit, the mass has stabilized at 2.3 mm in thickness while remaining stable in all other dimensions. She maintains 20/20 best corrected visual acuity after cataract surgery in both eyes. IOP in the affected eye has ranged between 12 mm Hg and 19 mm Hg.
For more information:
- Vivek Chaturvedi, MD, and Jay S. Duker, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.
- Edited by Isabel Balderas, MD, and Tom Hsu, MD. Drs. Balderas and Hsu can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com. Drs. Balderas and Hsu have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.
References:
- Conway RM, Chua WC, Qureshi C, Billson FA. Primary iris melanoma: diagnostic features and outcome of conservative surgical treatment. Br J Ophthalmol. 2001;85(7):848-854.
- Shields CL, Materin MA, et al. Factors associated with elevated intraocular pressure in eyes with iris melanoma. Br J Ophthalmol. 2001;85(6):666-669.
- Shields CL, Shields JA, et al. Iris melanomas: risk factors for metastasis in 169 consecutive patients. Ophthalmology. 2001;108(1):172-178.
- Shields JA, Sanborn GE, Augsburger JJ. The differential diagnosis of malignant melanoma of the iris. A clinical study of 200 patients. Ophthalmology. 1983;90(6):716-720.