Iris Melanoma

Description

This tapioca-colored iris tumor has pulled the iris pigment epithelium out onto the surface of the iris stroma.

Written by Paul T. Finger, MD

The iris is the colored part of the eye. It is made up of two layers. The outer "stroma" can be blue, hazel, green or brown. The back layer (the iris pigment epithelium) is always brown. Tumors can grow within and behind the iris. Though most iris tumors are cysts or nevi, malignant melanomas can also occur in the iris. 

Symptoms

Iris melanoma patients usually have no symptoms. The tumor might be noticed by the patient, their family, or by the eye care specialist (during a routine eye examination). Some people have lots of freckles on their irides. Some of these pigmented spots have thickness and are called Nevi.

If the patient notices that one of their nevi has changed, enlarged or is pulling (ovalization) on the pupil; they should see an eye care specialist for evaluation and possible referral to an eye cancer specialist.

Diagnosis

Photographs of the surface of the iris tumor should be obtained to establish a baseline for future comparisons. High frequency ultrasound is used to examine the depth of an iris tumor. Ultrasound can reveal if the tumor is cystic or solid, how it extends within the iris and ciliary body. Ophthalmic oncologists use high frequency ultrasound to diagnose and follow iris tumors for evidence of growth or regression after treatment.

High frequency ultrasound shows diffuse iris thickening with bowing and invasion of the iris pigment epithelium

Characteristics that suggest that an iris tumor is cancerous include seeing blood vessels within the tumor (intrinsic vascularity), secondary glaucoma, evidence that the pupil is deformed (ectropion uveae), and the development of a cataract beneath the tumor.

The most important finding is documented growth. Since iris melanomas are commonly small, and less commonly (10-11%) spread to other parts of the body, these tumors are typically watched for evidence of growth before biopsy or treatment is considered. A small amount of growth is not thought to significantly affect the rate of metastasis from iris melanoma.

A diffuse iris melanoma causing severe glaucoma was too large to remove or irradiate and was treated by enucleation.

When necessary, eye cancer specialists can use a small incision in the cornea to gain access to an iris tumor. A biopsy can usually tell if the tumor is benign or malignant.

Treatments

Most pigmented iris tumors do not grow. They are photographed and monitored with periodic observation. When an iris melanoma is documented to grow, we know that it can damage the eye and may cause secondary glaucoma. Then, treatment (despite its risks) becomes more reasonable.

Small Iris Melanomas:
Though most small iris melanomas can be surgically removed, the function of the iris and size of the pupil are better preserved after plaque radiation treatment.

Medium-sized Iris Melanomas:
Though many of these tumors can be surgically removed, plaque or proton radiotherapy should  be considered as primary treatment for these tumors. Though a radiation cataract is likely to develop, due to the distance between the radiation and the macular retina, vision limiting radiation retinopathy is very unlikely.

Large-sized Iris Melanomas:
These cases can often be difficult to treat with eye-sparing radiation therapy. However, many of these tumors cause untreatable glaucoma and may require removal of the eye.

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