Melanoma is an aggressive type of cancer that begins in cells called melanocytes. Melanocytes produce the pigment melanin and cause skin to become tan when exposed to ultraviolet (UV) light. Melanocytes can group together to form a mole, also called a nevus.
High levels of ultraviolet light exposure are associated with increased melanoma risk, so melanoma appears most often on parts of the body exposed to UV light emitted by the sun or by tanning beds. Rarely, melanoma begins in membranes lining the eye, sinuses, anus, or vagina. Although the exact relationship between UV radiation and melanoma remains unclear, researchers believe that melanoma can occur when radiation damages genetic material in the skin.
Approximately 68,000 people are diagnosed with invasive melanoma each year, according to the National Cancer Institute, though this disease is not as common as two other main types of skin cancer (basal cell carcinoma and squamous cell carcinoma). Early detection and treatment can lead to the best outcome.
Like melanoma of the skin, melanoma of the eye — or ocular melanoma — often begins with the appearance of an irregular mole, called a dysplastic nevus. More than 10 percent of the population will develop a mole in the eye during their lifetime, but only one in 5,000 of these moles will become cancerous. Our experts have extensive experience treating this rare disease.
Skin melanomas often look dark in color and asymmetrical, with a ragged or irregular border. Many are wider than a pencil eraser, but our doctors have advanced tools to detect even smaller melanomas. Although melanomas rarely lack pigment, they can sometimes appear as pink spots or bumps on the skin.
Medical experts from Memorial Sloan-Kettering discuss new strategies for preventing, diagnosing, and treating skin cancer.
The two main classifications of primary skin melanoma are in situ melanoma and invasive melanoma. In situ melanoma is confined to the upper layer of the skin, called the epidermis, and does not spread to other parts of the body after it is removed. Invasive melanoma enters the second layer of skin, called the dermis. This type of melanoma can spread to the lymph nodes and beyond, particularly if it is more than 1 millimeter thick. The deeper the disease penetrates the skin, the more likely it is to spread to other parts of the body, including nearby and distant lymph nodes, as well as the lungs, liver, brain, bones, and gastrointestinal tract.
Melanoma appears more often in adults, although this disease can affect children and adolescents as well. Extensive exposure to any level of UV radiation, intermittent exposure to high levels of UV radiation, or severe sunburns can increase your risk of developing melanoma. Other risk factors for melanoma include:
- Atypical moles — People with many moles or abnormal moles, called dysplastic nevi, are more likely to develop melanoma. Dysplastic nevi are often large and raised, with poorly defined borders and uneven colors that range from pink to dark brown. Irregular moles tend to run in families.
- Personal or family history of skin cancer — If you have already been diagnosed with melanoma or another form of skin cancer, you are at a significant risk of developing a second skin cancer. You are also at a higher-than-average risk for melanoma if you have two or more relatives who have been diagnosed.
- Light complexion or fair skin — People with any color skin can develop melanoma, though those who have light complexions are at a higher risk — especially if you have had excessive exposure to UV radiation.
- Weakened immune system — If your immune system has been weakened by AIDS, immunosuppressive drugs, or certain cancers, you have a higher-than-average risk of developing melanoma.
- Other skin conditions — If you have xeroderma pigmentosum, a rare inherited condition in which the body cannot repair the DNA of skin cells damaged by UV radiation, you are at greater risk for melanoma.
The best way to prevent melanoma is to protect your skin from the sun and avoid extended periods of sun exposure. If you are a parent, you can reduce your children's risk of skin cancer by protecting their skin and teaching them sun-safe behavior. Everyone should avoid sunlamps, tanning beds, and tanning booths, which are potentially dangerous sources of harmful UV radiation. When outdoors, wear clothing and hats that cover exposed skin, wear glasses with UV protection, and apply a broad-spectrum sunscreen that blocks the two main types of radiation: UVA and UVB.
Memorial Sloan-Kettering researchers are among the leaders of an international collaboration, sponsored by the National Cancer Institute, to investigate the genetic and environmental factors that contribute to melanoma susceptibility. Our researchers aim to define the genetic factors that make some people more likely than others to develop melanoma. The project is focusing on mutations in genes that protect the body from the effects of UV radiation and on genes that regulate the life cycle of cells.
The eye is the second most common location of melanoma. Ocular melanoma can affect many parts of the eye, including the eyelids, the clear conjunctiva that covers the eye's surface and the inside of the eyelids, and most commonly the uveal tract. This area includes the colored iris surrounding the pupil; the ring-shaped ciliary body, which changes the shape of the lens for focusing; and the pigmented choroid layer, beneath the retina. Melanoma of the choroid is the most common type of eye melanoma.
Risk factors for ocular melanoma are similar to the risk factors for skin melanoma, such as:
- fair skin that is frequently sunburned or does not tan
- light-colored eyes
- older age
- European descent, especially northern Europe
- working as a welder without proper eye protection
Recently, Memorial Sloan-Kettering researchers also identified mutations in genes called GNAQ and GNA11 that have been associated with more than 40 percent of uveal melanoma cases.(1)
Because ocular melanoma has few early symptoms, doctors are most likely to diagnose this disease during a routine eye exam. Most people who have ocular melanoma only experience symptoms when the tumor has become large enough to interfere with vision. However, symptoms such as blurred or changed vision, a dark spot on the eyelid or iris, or a change in the pupil's shape can be early signs of melanoma in the eye.
If left undetected and untreated, melanoma of the eye can spread through the bloodstream to other organs.