Cancer is when cells in the body change and grow out of control. To help you understand what happens when you have cancer, let's look at how your body works normally. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).

Primary eye cancer is a very rare kind of cancer that starts somewhere in or on the eye (on the surface, on the iris, or within the eye beneath the retina) or in the skin of cells around the eye (the eyelid). It’s very rare. So it’s best for someone with eye cancer to get treatment from someone who specializes in this field. A person can ask their healthcare provider to refer them to an eye cancer specialist.

There are different kinds of eye cancers. Below are some of the more common ones:

• Intraocular melanoma (uveal melanoma). This is the most common type of eye cancer. It often develops in the choroid or ciliary body.

• Intraocular lymphoma. A very rare type of lymphoma (typically non-Hodgkin) that starts in the eyeball.

• Eyelid tumors. Basal cell carcinoma, a type of skin cancer, is the most common type of eyelid cancer. It can be removed with surgery. Other types of eyelid tumors include squamous cell carcinoma, sebaceous cell carcinoma, and malignant melanoma.

• Conjunctival tumors. These are tumors that grow on the surface of the eye. These tumors include squamous carcinomas, melanomas, and lymphomas.

• Lacrimal gland tumors. Tumors found in the tear glands.

• Retinoblastoma. This cancer of the eye is the most common type in children. It's extremely rare in adults.

The eye is an organ that collects light and sends it to the brain. The brain turns this light from the eye into pictures that let you see. The eye is made up of many different parts:

• Eyelids. These keep the eyes moist and shield them from light.
• Conjunctiva. This is a membrane that covers the eyeball and lets the eyelid slide easily over the eye without irritating it.
• Cornea. This is the clear window that helps focus light and covers and protects the iris.
• Iris. This is the colored part of the front of the eye. It adjusts the size of the opening in the middle of the iris (the pupil).
• Retina. This lines the inside of the eye. It does the work that helps people to see.
• Choroid. This is a layer of blood vessels under the retina. The choroid feeds the retina. It also has cells in it called melanocytes. These cells can sometimes grow into a cancer called melanoma.
• Ciliary body. This makes a watery fluid that is between the cornea and the iris. It also has muscles to control the shape of the eye lens. It does this to adjust to the distance of the objects you focus on.
• Uvea. This is a layer of tissue under the white of the eye (sclera). The uvea is made up of the choroid, the iris, and the ciliary body.

If you have questions about eye cancer, talk with your healthcare provider. Your healthcare provider can help you understand more about this cancer.