Risk factors for eye cancer
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes eye cancer develops in people who don’t have any of the risk factors described below.
In general, Caucasians tend to be affected by eye cancer more often than people of other ethnicities. In Canada, the number of new cases of eye cancer diagnosed each year (called the incidence) starts to increase in people in their early 30s. Eye cancer generally affects men and women equally, but after the age of 50 it occurs more often in men.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
Known risk factors
There is convincing evidence that the following factors increase your risk for eye cancer.
Primary acquired melanosis (PAM) is a condition of the conjunctiva, which is a clear mucous membrane that covers the inner surface of the eyelids and the outer surface of the eye. It appears as a flat, brown patch that has a high number of melanocytes in it. Melanocytes are the cells that produce melanin, which is the substance that gives colour to our skin, hair and eyes.
PAM mostly affects Caucasians. It increases the risk of melanoma of the conjunctiva, a type of eye cancer.
Ocular melanocytosis (also called oculodermal melanocytosis or nevus of Ota) is a rare condition of the eye that is present at birth. People with this condition have a high number of melanocytes and more melanin than normal in and around their eyes.
Ocular melanocytosis increases a person’s risk of developing intraocular melanoma, the most common type of eye cancer.
People with fair or light-coloured skin have a higher risk of developing intraocular melanoma than people with other skin types. People with blonde or red hair and blue, green or grey eyes also have a higher risk of developing intraocular melanoma. Their risk is greater because people with these features have less melanin. Melanin is what gives colour to your skin, hair and eyes. Experts think that it also helps protect the skin from ultraviolet radiation (UVR).
A mole is a non-cancerous growth on the skin that is usually tan, brown or flesh-coloured. They are not usually present at birth, but often begin to appear in childhood. People with skin moles have a higher risk of developing intraocular melanoma in the uvea (called uveal melanoma). The uvea is the middle layer of the wall of the eye, which is the outer part of the eyeball.
Having atypical skin moles increases the risk of developing intraocular melanoma. An atypical skin mole (also known as a dysplastic nevus) looks different from a normal mole. Many atypical moles are at least 5 mm (which is larger than a normal mole), have an irregular shape and have undefined borders.
Having familial atypical multiple mole melanoma (FAMMM) syndrome also increases the risk of developing intraocular melanoma. FAMMM (sometimes called dysplastic nevus syndrome) is an inherited condition in which people have a large number of moles on their body.
Tanning beds and sun lamps give off ultraviolet radiation (UVR), which can damage the eyes and increase the risk for intraocular melanoma.
Welders have a higher than average risk of developing eye cancer, particularly intraocular melanoma. This increased risk is likely due to exposure to ultraviolet radiation (UVR) from welding tools. It could also be due to exposure to other harmful agents in the workplace.
People who are infected with the human immunodeficiency virus (HIV) or have acquired immunodeficiency syndrome (AIDS) have a higher risk of developing the following types of eye cancer:
- lymphoma of the eye
- squamous cell carcinoma of the conjunctiva
The higher risk for these cancers may be because the virus weakens the immune system or affects the body in other ways.
The following factors have been linked with eye cancer, but there is not enough evidence to show they are known risk factors. More research is needed to clarify the role of these factors for eye cancer.
The sun is the main source of ultraviolet radiation (UVR). Sun exposure is a known risk factor for melanoma of the skin. Research has also linked it to melanoma of the eye (called intraocular melanoma) and squamous cell carcinoma of the conjunctiva.
Scientists believe sun exposure might be a risk factor for eye cancer for several reasons. They note that melanoma develops in the areas of the eye that receive the most sunlight. They also point out that melanoma of the eye and melanoma of the skin share some risk factors, such as having light-coloured skin or eyes. Some evidence also suggests that people who work outside have a higher risk of developing eye cancer.
Like a skin mole, an eye mole (also called an ocular nevus) is non-cancerous. But people who have eye moles may have a higher risk of developing melanoma of the eye.
Changes, or mutations, to certain genes have been linked to a higher risk of developing eye cancer. Researchers continue to study genes to find out which ones may be involved with the development of eye cancer.
BAP1 gene mutation
The BAP1 gene is also called the BRCA1 associated protein 1 gene. It is a type of gene that helps control cell growth and may limit the growth of cancer cells (called a tumour suppressor gene). A mutation in the BAP1 gene may increase the risk for uveal melanoma, as well as mesothelioma and melanoma of the skin. Healthcare professionals may refer to people who have the BAP1 gene mutation as having BAP1 cancer syndrome.
GNA11 gene mutation
The GNA11 gene makes a protein that helps control cell growth and the normal process of programmed cell death (called apoptosis). It is found in certain types of cells, including those in the eyes, skin, heart and brain. A mutation in the GNA11 gene may increase the risk for uveal melanoma.
Family history of intraocular melanoma
Some families have more cases of intraocular melanoma than would be expected by chance. A family history of intraocular melanoma means that one or more close blood relatives have been diagnosed with the disease. Sometimes it is not clear if the family’s pattern of cancer is due to chance, shared lifestyle factors, a hereditary factor (such as having the BAP1 gene mutation) or a combination of these factors.
BAP1 cancer syndrome is an inherited syndrome that has been linked to an increased risk of uveal melanoma, a type of intraocular melanoma.
People who work in the chemical industry (including chemists, chemical engineers and chemical technicians) or in the cooking industry may have a higher risk of developing eye cancer. More research is needed to understand how working in these industries increases the risk.
Having freckles, especially as a child, may increase your risk for eye cancer. The link between having freckles and eye cancer may be explained by UVR from the sun, which can contribute to freckling.
Unknown risk factors
It isn’t known whether or not the following factors are linked with eye cancer. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if the following are risk factors for eye cancer:
- having a personal history of melanoma of the skin
- having a family history of breast or ovarian cancer (the risk for eye cancer may be related to a BRCA2 gene mutation)
- taking drugs that weaken the immune system (called immunosuppressants)
- being infected with human papillomavirus (HPV), which may be linked to squamous cell carcinoma of the conjunctiva
- being infected with Chlamydophila psittaci (C. psittaci), which may be linked to intraocular lymphoma
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about risks.
The thin, moist layer of tissue that lines some organs and body cavities, including the nose, mouth, lungs, airways, vagina and gastrointestinal (GI) tract.
Glands in the mucous membrane make mucus (a thick, slippery fluid).
Also called mucosa.
Passed from parent to child through information contained in genes.
Also referred to as inherited.
BRCA1 and BRCA2 genes are tumour suppressor genes. Changes to genes are called mutations. Mutations of the BRCA genes are inherited from one or both parents, and these mutations increase the risk of cancer.
Women with BRCA mutations have a higher risk of breast and ovarian cancers. Men with BRCA mutations also have a higher risk of breast cancer, and may have a higher risk of prostate cancer. The risk of other cancers – such as stomach or pancreatic cancer – may also be higher with BRCA mutations.
What’s the lifetime risk of getting cancer?
The latest Canadian Cancer Statistics report shows about half of Canadians are expected to be diagnosed with cancer in their lifetime.