Melanoma begins in the melanocytes, the cells that make melanin which is the pigment that determines your natural skin color.
Melanoma is much more serious than the other more common types of skin cancers such as basal and squamous cell carcinomas. Melanoma can spread quickly to other organs and causes the vast majority of skin cancer deaths in the United States.
Melanomas usually develop in or around an existing mole. Since the cells usually continue to make melanin, melanoma tumors are often brown or black. They usually occur on the skin of the trunk or extremities, but they can occur elsewhere, such as in the eye (ocular or uveal melanomas) or in the lining of nose/mouth/gut (mucosal melanomas). Rarely, melanoma shows up in the meninges (the membrane that covers the brain and the spinal marrow), lymph nodes, or other areas where melanocytes are found.
In its earliest stage, melanoma begins as “melanoma in situ,” meaning it doesn’t grow much beyond the epidermis (the most superficial layer of the skin). If it is not removed when it is thin, melanoma can penetrate (invade) deeper into the skin and may also spread throughout the body.
Types and pictures of melanoma
There are four basic types of melanoma. The first three types are “in situ,” which is Latin for “localized.”
- Superficial spreading melanoma. This is the most common type of melanoma and accounts for about 70 percent of all melanomas. It travels along the top layer of the skin for a long time before going deeper into the skin. It can be found almost anywhere on the body, but is most likely to be on the trunks of men, legs of women, and upper backs of both. Superficial spreading melanoma mostly affects adults but young people develop it as well.
Appearance: The first sign is a flat or slightly raised, somewhat geometrical, discolored patch with irregular borders. The color varies, with possible areas of tan, brown, black, red, blue, or white. Sometimes an older mole will turn into this kind of melanoma.
- Acral lentiginous melanoma. This melanoma also spreads superficially before growing deeper into the skin. It is usually found under the nails, on the soles of the feet, or the palms of the hands. Acral lentiginous melanoma is the most common melanoma in African-Americans and Asians, and the least common among whites.
Appearance: It appears as a black or brown discoloration.
Lentigo maligna. This melanoma is similar to the superficial spreading type. It stays close to the skin’s surface for a long time, but becomes invasive more quickly than the other two. This melanoma is most often found in elderly people, showing up on the face, ears, arms and upper trunk—skin chronically exposed to and damaged by sun exposure. Lentigo maligna is the most common form of melanoma in Hawaii.
Appearance: Usually appears as a flat or mildly elevated mottled tan, brown or dark brown discoloration.
Nodular melanoma. This fourth kind of melanoma is usually already invasive when first diagnosed. This very invasive cancer is commonly located on an older person’s trunk, legs, and arms and on the scalp of men at any age.
Appearance: This malignancy is recognized when it becomes a bump, most often black, but occasionally blue, gray, white, brown, tan, red, or skin tone.
Images courtesy of Gregory J. Raugi MD, PhD, Professor, University of Washington Medicine.