University of Iowa Health Care

Ophthalmology and Visual Sciences

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Iris Melanocytoma

Contributor:  Thomas J.E. Clark, MD

Photographers:  Antoinette Venckus, CRA (fig. 1); and Wallace L.M. Alward, MD (fig. 2)

A melanocytoma is a specific type of uveal tract nevus, termed "magnocellular nevus", characterized clinically by its jet-black coloration and histologically by its heavily pigmented, large, polygonal, bland cells.  Clinically, melanocytomas most often present as asymptomatic pigmented lesions. 

Melanocytomas can occur anywhere along the uveal tract, but are most commonly found in the juxtapapillary region of the choroid (see related links).

Traditionally viewed as benign lesions, transformation into a malignant melanoma can occur.  Malignant transformation rates for choroidal melanocytomas have been reported at 2%.(1)


Figure 1: Slit lamp examination, demonstrates a dark brown, pigmented lesion in the peripheral iris extending from 6:30 to 8 o'clock.  Notably, there is no neovascularization of the iris and the pupil is round. Diagnosis was confirmed by biopsy.

a dark brown, pigmented lesion in the peripheral iris extending from 6:30 to 8 o'clock

Slit lamp image, additional view

slit lamp image, narrow beam


Figure 2: Gonioscopy examination demonstrates an elevated, dark brown lesion extending from 7 to 8 o'clock without spread into the surrounding trabecular meshwork.

an elevated, dark brown lesion extending from 7 to 8 o'clock without spread into the surrounding trabecular meshwork


Figure 3: B-scan ultrasonography shows an iris lesion with low internal reflectivity and no vascularity.

b-scan image


Related Links:  

Reference

  1. Shields JA, Demirci H, Mashayekhi A, Shields CL. Melanocytoma of optic disc in 115 cases: the 2004 Samuel Johnson Memorial Lecture, part 1. Ophthalmology 2004;111:1739-46.

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last updated: 12/23/2015

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