domingo, 25 de noviembre de 2018

What is eye cancer?

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By Ananya Mandal, MDReviewed by April Cashin-Garbutt, MA (Cantab)

Eye cancer, as the name suggests begins in the eye. The eye is composed of various smaller structures each of which can be affected.

A cancer or tumor is basically an uncontrolled growth of any particular cell or group of cells. This tumor may be benign (non-cancerous) or malignant (cancerous).

Cancerous tumors are fast growing, fast spreading and may be fatal if not treated. Eye cancers like other eye diseases are treated by Ophthalmologists and oncologists (cancer specialists).

Anatomy of the eye

The normal eye has three basic parts (1, 2) –

The eyeball or the globe. It is filled with jelly like material called the vitreous humor.

Associated structures of the eye. These include –

Conjunctiva – the thin transparent cover over the eye
The sclera – the tough covering of the eyeball or the whites of the eyes
The uvea middle layer covering of the eye ball. It has three parts –

The pupil and the iris that act as light apertures
The ciliary body that regulates the papillary opening
The chorid that is pigmented and nourishes the retina

The retina that forms the picture Cornea – the clear transparent layer over the pupil that lets in light
The lens the crystalline non-cellular and hard organ that allows sight
The optic nerve that carries the information of the picture from the retina to the brain for sight.

The orbit or the cavity that carries the eyeball
Adnexal structures like eyelashes, tear glands etc.

Types of cancer

Cancers of the eyes may be of two main types: intraocular and adnexal (1, 2) –

Intraocular –

Primary intraocular – those cancers that begin inside the eyeball. These include Melanoma, Primary intraocular lymphoma, retinoblastoma, medulloepithelioma.

A melanoma is the commonest type of primary intraocular cancer in adults. It starts in the colored or pigmented cells of the eye and multiplies fast and uncontrollably.

Melanoma can affect several parts of the eye – the Uvea, Choroid or the Conjunctiva.

Uveal melanoma is by the commonest form of intraocular melanoma. It can affect the choroid, ciliary body as well the iris. It is usually a slow growing tumor and has a good treatment outcome. Uveal melanoma rarely spreads to other parts.

Conjunctival melanoma is a tumor of the conjunctiva. It spreads fast to other parts via lymphatic channels. It is a rare form of melanoma of the eye.

Choroid melanoma is less common. (3)

Intraocular lymphoma is generally a rare condition and is believed to be almost always a form of central nervous system lymphoma or Non-Hodgkin’s lymphoma.

Lymphomas in general may be Hodgkin’s or Non-Hodgkin’s in type. While Hodgkin’s lymphoma affects the blood, Non-Hodgkin’s lymphoma may affect other sites such as the brain, lungs or eyes.

These usually begin in immune system cells called lymphocytes. They usually affect the elderly or individuals who have low immunity or other immune system problems like those affected by acquired immunodeficiency syndrome (AIDS).

Retinoblastoma is a childhood eye cancer. It affects the retina. A hemangioma is a tumor of blood vessels of the eye. This is rare.

Secondary intraocular – These cancers begin at a different location and spread to the eye. Common distant cancer sites that may lead to secondary eye cancers are lung and breast cancers.

Adnexal

Adnexal or orbital cancers – These cancers affect the adnexa (surrounding structures) or the orbit. They mainly affect the skin, muscles and nerves around the eyeball.

Eyelid carcinoma may affect the skin and muscles of the eyelid and may be surgically removed when detected. These are basically squamous or basal cell type of skin cancers.

Lacrimal gland tumors affect the tear glands. These cancers are usually similar in pathology with other skin cancers.

Their growth rate, malignancy and ability to spread is also akin to skin cancers. If detected early these cancers can be removed surgically and offer a good prognosis or outcome.

Although eye cancers and tumors are rarely fatal if detected early, they can result in loss of vision.

Secondary eye cancers from other primary cancers may also result in vision loss. The primary aim of therapy is survival and efforts are made to preserve the eyesight.