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We've discussed the ocular neoplasms.

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of childhood and infancy.

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Let's talk about the ocular neoplasm of adulthood.

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The most common cause of ocular tumor

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in the adult is a choroidal melanoma.

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Choroidal melanomas may occur associated

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with the choroid or

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the uveal tract, because there is pigmented epithelium

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which extends to the iris of the eye.

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So one can see it in the uveal tract or along

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the posterior membranes of the choroid.

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This is a tumor that shows contrast enhancement,

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as you see here.

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This is a contrast-enhanced study as you can tell from

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the cavernous sinus,

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and is showing contrast

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enhancement tumor in the right eye.

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The differential diagnosis in an adult

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would include metastases.

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Metastases to the ocular membranes,

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something that is not infrequently seen on pathology

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slides and includes those typical tumors that

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we would expect that show metastases,

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including breast and lung cancer.

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However, they rarely will present clinically.

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With respect to uveal melanoma or choroidal melanoma,

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there are some important findings

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that should be pointed out.

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Those findings include the fact that this is a disease

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that affects adults, and it is a disease that

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may show amelanotic and melanotic forms.

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This is important with respect to MRI scanning.

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Melanin is paramagnetic. And therefore, a melanotic

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melanoma, one that has melanin within it, may

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be bright on a T1-weighted scan,

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pre-contrast when looking at the orbit and

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depending upon its melanin content,

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may actually be dark in signal intensity on

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T2-weighted scan.

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However, amelanotic melanomas,

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which also can occur in the choroid,

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will be dark on T1-weighted scan

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and bright on T2-weighted scan.

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Whether it's amelanotic or melanotic, it's a tumor of

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the globe that will show contrast enhancement.

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It is a tumor of the globe which is occurring more

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commonly in caucasian patients and there is a high rate

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of retinal detachment associated

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with choroidal melanomas.