Introduction to Eye Cancer

Executive Summary

Eye cancer develops tumour formation in different parts of the eye. Cancer that forms in the eyeball is an intraocular (inside the eye) malignancy. Eye cancer is very rare, and it affects the outer parts of the eye, such as the eyelid, which are made up of muscles, skin and nerves. Cancer originating from the eyeball is called intraocular cancer. The most common eye cancer in children is retinoblastoma, which starts in the retina cells, while in adults, the most common intraocular cancers are lymphoma and melanoma. The most common intraocular cancer is uveal metastases in adults, which have spread to the uvea from other places in the body. Melanoma is the most common type of primary intraocular cancer in adults, originating from cells called melanocytes that grow uncontrollably. Different less common types of intraocular tumour include Intraocular lymphoma, retinoblastoma, and hemangioma. The rare type of eye cancer includes conjunctival melanoma, eyelid carcinoma, and lacrimal gland tumour.

What is Eye Cancer?

Eye tumour is a generalized term used for tumours that start in various parts of the eye. Tumors can be benign or cancerous. A benign tumour remains confined to its original location. A cancerous tumour can grow and spread to other parts of the body. Cancer that forms in the eyeball is an intraocular (inside the eye) malignancy. A malignancy is a group of cancer cells. They are non-typical cells that grow quickly and uncontrollably.

Cancer is uncommon in the eye. It can affect the outer parts of the eye, like the eyelid, which are made up of muscles, skin and nerves [1]. If cancer starts inside the eyeball, it's known as intraocular cancer. The most common eye cancer in children is retinoblastoma, which starts in the retina cells, while in adults, the most common intraocular cancers are lymphoma and melanoma.

Parts of the eye

The eye gathers the light and transmits the message to the brain to form a picture. The three parts of the eye are -

• Eyeball
• Orbits (eye sockets)
• Accessory structures like eyelids and tear gland

The outer eye consists of the sclera, retina and uvea. The sclera is the outermost wall of the eye. The retina is a thin-layered structure lining the eyeball and sends information to the brain through the optic nerve. The uvea nourishes the eye. Both the retina and uvea have blood vessels.

The uvea consists of :

• Iris - Coloured part of the eye controlling the amount of light entering the eye.
• Ciliary body- It is a muscular tissue that secretes watery fluid and helps the eye focus.
• Choroid - The layer of tissue underneath the retina containing melanocytes and connective tissue. The choroid is the most common site for tumours.

Types of Intraocular Cancer

The most common intraocular cancer is uveal metastases in adults, which have spread to the uvea from other places in the body. This is known as secondary cancer [2].

In adults, melanoma is the most common type of primary intraocular cancer. It began when cells called melanocytes grew uncontrollably. Intraocular melanoma is also called uveal melanoma.

Other, less common types of intraocular tumor include [3]:

• Intraocular lymphoma is lymphoma that starts in the eyeball. This condition is rare and is difficult for doctors to diagnose. Many doctors consider intraocular lymphoma a type of central nervous system lymphoma. Most intraocular lymphomas are non-Hodgkin lymphoma.
• A retinoblastoma is a rare form of childhood eye cancer.
• Hemangioma is a benign tumour of the choroid and retina that starts in the blood vessels.

Other rare cancers of the eye include [4]:

• Conjunctival melanoma is a tumour of the conjunctiva, a membrane that lines the eyeball and eyelid. If not treated, it can spread to the tiny lymph nodes bean-shaped organs that fight disease throughout the body. A conjunctival melanoma tends to recur on the eye's surface and looks like dark spots on the eye. Doctors usually do a biopsy on a spot that appears to be conjunctival melanoma. A biopsy removes a sample of the tissue for examination under a microscope.
• Eyelid carcinoma (squamous or basal cell) is a variation of skin cancer. This tumour may be surgically removed and is usually not dangerous if treated early.
• A lacrimal gland tumour is a benign or malignant tumour of the glands that produce tears.

References

1. 1.

   Maheshwari A, Finger PT. Cancers of the eye. Cancer Metastasis Rev. Published online September 10, 2018:677-690. doi:10.1007/s10555-018-9762-9

2. 2.

   Harbour JW. Eye Cancer: Unique Insights into Oncogenesis The Cogan Lecture. Invest Ophthalmol Vis Sci. Published online May 1, 2006:1737. doi:10.1167/iovs.05-1291

3. 3.

   Bornfeld N, Biewald E, Bauer S, Temming P, Lohmann D, Zeschnigk M. The Interdisciplinary Diagnosis and Treatment of Intraocular Tumors. Deutsches rzteblatt international. Published online February 16, 2018. doi:10.3238/arztebl.2018.0106

4. 4.

   Eagle RC Jr. The pathology of ocular cancer. Eye. Published online November 16, 2012:128-136. doi:10.1038/eye.2012.237