Melanoma is a deadly cancer that arises from the pigment-producing cells in the body, called melanocytes. Melanoma occurs most frequently on the skin and in the eyes.
Skin (Cutaneous) Melanoma
Cutaneous melanoma is the most lethal form of skin cancer, leading to nearly 10,000 deaths each year in the United States and 49,000 deaths each year worldwide. The overall rate of new skin melanomas diagnosed annually in the country has tripled since the 1970s, although doctors are detecting and treating many melanomas earlier than before.
Any person, regardless of skin color, race, ethnicity, sex, or age, can develop melanoma. Knowing the risk factors and early signs of melanoma is important because patients, not physicians, detect the majority of skin melanomas.
Skin melanoma is broadly categorized as either in situ or invasive disease.
- In situ melanoma is confined to the most superficial layer of the skin, known as the epidermis, and has an excellent overall prognosis. This form of melanoma can often be cured through simple skin surgery.
- Invasive melanoma has penetrated the epidermis and entered the second layer of the skin, called the dermis. Although any invasive melanoma can metastasize and spread to lymph nodes or distant body sites, the risk of metastasis is related to the depth of invasion. Treatment of invasive melanoma is based on the American Joint Commission of Cancer (AJCC) stage at diagnosis.
Eye (Ocular) Melanoma
The second most common location of melanoma is in the eye. Many parts of the eye can be affected, including:
- the eyelids;
- the clear conjunctiva that covers the eye’s surface and the inside of the eyelids (called conjunctival melanoma);
- the eye’s middle layer that includes the colored iris surrounding the pupil, the ring-shaped ciliary body that changes the shape of the lens for focusing (called iris melanoma);
- and the pigmented choroid layer beneath the retina (choroidal melanoma, the other type of uveal melanoma). Choroidal melanoma is the most common type of eye melanoma.
Melanoma of the eye is often identified following the appearance of an irregular mole, called a dysplastic nevus. More than one in ten people will develop a mole in the eye at some point, but only one in 5,000 of these moles will become cancerous.