Melanoma starts in the body’s pigment-producing cells, called melanocytes. The areas of the body that are most commonly affected are the skin and the eyes (called ocular melanoma).
Many skin melanomas are thought to occur when ultraviolet (UV) light — both from the sun and from indoor tanning beds or booths — damages the genetic material in the melanocytes. It’s also possible for melanoma to develop in parts of your body not exposed to sunlight, such as the membranes lining your eyes, sinuses, anus, or vagina, though this is relatively rare.
Any person, no matter their skin color, race, ethnicity, gender, or age, can develop melanoma. Knowing the risk factors and early signs of the disease is important because you — not your doctor — will most often notice melanoma first.
Skin melanomas fall into one of two categories:
- In situ melanoma affects the outermost layer of your skin, known as the epidermis. This form of melanoma can often be cured through simple surgery and has an excellent overall prognosis.
- Invasive melanoma, which has grown through the epidermis and entered the second layer of the skin (the dermis), is a serious condition. The risk with invasive melanoma is that it will spread to lymph nodes or other parts of the body.
Melanoma can affect many parts of your eyes, including:
- the pigmented layer beneath the retina (choroidal melanoma, which is the most common type of eye melanoma)
- the eyelids
- the clear conjunctiva, which covers the eye’s surface and the inside of the eyelids (conjunctival melanoma)
- the eye’s middle layer, which includes the colored iris surrounding the pupil (iris melanoma)
Many people receive a diagnosis of eye melanoma when a doctor finds an irregular mole on their skin, called a dysplastic nevus. While more than one in ten people develop a mole in the eye at some point, only one in 5,000 of those moles becomes cancerous.