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Eye cancer can refer to any cancer that starts in the eye. The most common type of eye cancer is melanoma (also known as ocular melanoma or intraocular melanoma). But there are other types of cancer that affect different kinds of cells in the eye.

Where eye cancers start

The eye has 3 major parts:

• The eyeball (globe), which is mostly filled with a jelly-like material called vitreous humor and has 3 main layers (the sclera, the uvea, and the retina)
• The orbit (the tissues surrounding the eyeball, also called the eye socket)
• The adnexal (accessory) structures such as the eyelids and tear glands

Different types of cancer can start in each of these areas.

Types of eye cancer (intraocular cancers)

Cancers that are ?within the eye itself are called intraocular (or ocular) cancers:

• Primary intraocular cancers start in the eye.
• Secondary intraocular cancers start in another part of the body and spread to the eye.

In adults, the most common primary intraocular cancers are:

• Melanoma (Intraocular melanoma is the focus of our information on eye cancer.)
• Non-Hodgkin lymphoma (See Non-Hodgkin Lymphoma for more information on primary intraocular lymphoma.)

In children, the most common primary intraocular cancers are:

• Retinoblastoma, a cancer that starts in cells in the retina (the light-sensing cells in the back of the eye)
• Medulloepithelioma, which is extremely rare

These childhood cancers are discussed in Retinoblastoma.

Secondary intraocular cancers (cancers that start somewhere else in the body and then spread to the eye) are not truly “eye cancers,” but they are actually more common than primary intraocular cancers. The most common cancers that spread to the eye are breast and lung cancers.

Intraocular melanoma (melanoma of the eye)

Intraocular melanoma, or ocular melanoma, is the most common eye cancer in adults, but it is still fairly rare. Melanomas that start in the skin are much more common than melanomas that start in the eye.

Melanomas develop from pigment-making cells called melanocytes. In the eye, they usually start in the uvea (uveal melanoma) or much less often in the conjunctiva (conjunctival melanoma).

Uveal melanomas

The uvea is the middle layer of the eyeball. It has 3 main parts:

• The iris is the colored part of the eye. It surrounds the pupil, the small opening where light enters the eye.
• The ciliary body contains the muscles inside the eye that change the shape of the lens so that the eye can focus on near or distant objects. It also has cells that make aqueous humor, the clear fluid in the front of the eye between the cornea and the lens.
• The choroid is a thin, pigmented layer lining the eyeball that nourishes the retina and the front of the eye with blood.

Choroidal melanoma: Most uveal melanomas begin in the choroid. Choroid cells make the same kind of pigment as melanocytes in the skin, so it’s not surprising that these cells sometimes form melanomas.

Ciliary body melanoma: The next most frequent type of uveal melanoma begins in the ciliary body. The ciliary body is located behind the iris, so tumors in this area can often grow for a long time without being found. This means these tumors are usually larger when diagnosed. Ciliary body melanomas are more likely to spread outside the eye than choroidal and iris melanomas.

Iris melanoma: Most other intraocular melanomas start in the iris. These are the easiest for a person or their doctor to see because they often start in a dark spot on the iris. Often, this spot has been present for many years and then begins to grow. These melanomas usually are slow growing, and they rarely spread to other parts of the body. For these reasons, people with iris melanomas generally have a good prognosis (outlook).

Uveal melanomas can spread through the blood, most often to the liver.

Conjunctival melanomas

The conjunctiva is a thin clear covering over the sclera, which is the white part of the eyeball.

Conjunctival melanomas are rare. They often look like a raised, brown or black spot on the white part of the eye, although sometimes they lack color. Conjunctival melanoma tends to grow more quickly than uveal melanoma, and it also tends to come back (recur) after treatment. This type of eye melanoma is treated differently.

Orbital and adnexal cancers

Orbital cancers develop in the tissues surrounding the eyeball, called the orbit. These include the muscles that make the eye move, the nerves attached to the eye, the bones that surround it, and nearby blood vessels.

Adnexal cancers start in the accessory (adnexal) structures such as the eyelids and tear glands.

Cancers of the orbit and adnexa are rare. They develop from tissues such as muscle, nerve, bone, blood vessels, or skin around the eyeball and are like cancers that start in these tissues in other parts of the body. For example:

• Eyelid cancers are usually skin cancers.
• Cancers affecting the eye muscles are usually rhabdomyosarcomas.