Which ocular exam findings are characteristic of iris melanoma?

Updated: Jul 13, 2021
  • Author: Buraa Kubaisi, MD, FICO, MRCS(Edin); Chief Editor: Michael Taravella, MD  more...
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Answer

Answer

Iris melanomas may be circumscribed or diffuse. Circumscribed melanomas have a nodular shape, and almost 80% arise in the inferior half of the iris (see image below). [7]  They vary in size, shape, and clinical behavior. They are typically yellow, tan, or brown in color with a flat or rounded anterior contour. [1]  They can grow anteriorly into the anterior chamber or posteriorly into the posterior chamber, usually being limited by the lens and giving a “lion’s paw” appearance on ultrasonographic biomicroscopy (UBM).

Inferior iris melanoma of the left eye that is pus Inferior iris melanoma of the left eye that is pushing the pupil superiorly and nasally and distorting the normal appearance of the iris. Image courtesy of MERSI, Waltham, MA.

Diffuse melanomas present differently from circumscribed melanomas, usually as a unilateral dark iris (acquired heterochromia) without focal thickening. [8] Diffuse melanoma may also be associated with glaucoma, which tends to respond poorly to medical management and causes severe disc cupping and functional loss. Diffuse melanomas also tend to be of the epithelioid cell type and carry a higher risk of metastasis than do circumscribed melanomas. Distant metastasis occurs in 13% of patients with diffuse iris melanomas. [8]

General signs indicative of malignant transformation include rapid growth of the lesion and the development of prominent blood vessels.

Ring melanomas involve more than two thirds of the angle and have associated glaucoma. Tapioca melanomas are multifocal nodules projecting into the anterior chamber that may be associated with glaucoma.


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