There are four main types of melanoma of the skin (called cutaneous melanoma), based on their location and their appearance under a microscope. These include a rare but especially dangerous kind that typically affects African-Americans and other people of color. Three of these varieties of melanoma initially form in just the top layer of skin (referred to as in situ). The fourth is invasive from the beginning, meaning it has penetrated deeper layers of skin and thus is more likely to spread to lymph nodes or other organs more rapidly. (1) Other parts of the body, such as the eyes and mucosal linings, can also develop melanoma. These rare cancers can be especially difficult to diagnose and treat.
Superficial Spreading Melanoma
Accounting for 70 percent of all cases of skin melanoma, this is the kind most younger people develop. As the word “superficial” in the name suggests, it develops across the top layer of skin before growing deeper. Superficial spreading melanoma typically develops on the chest and back in men and on the legs in women. The head and neck are also common sites. Research has found that melanoma in these parts of the body is twice as likely to prove fatal as melanoma identified elsewhere. (1) Tumors can be brown, black, tan, red, blue, or white. Some may develop from a formerly benign (harmless) mole. They may look like a flat or slightly raised discolored patch with irregular borders and a somewhat asymmetrical shape.
Lentigo Maligna
This melanoma tends to develop in elderly people on parts of the body that have been habitually overexposed to the sun — typically the face, ears, arms, and upper trunk (chest and upper back). Like superficial spreading melanoma, lentigo maligna grows more slowly across the top layer of skin, looking like a flat or slightly raised tan, brown, or dark-brown patch. It is the most commonly diagnosed form of melanoma in Hawaii. (1)
Acral Lentiginous Melanoma
This third main form of melanoma typically affects hairless skin. It may appear as a black or brown mark underneath the fingernails or toenails, on the sole of the foot, or on the palm of the hand. Acral lentiginous melanoma (ALM) tends to be more aggressive and less responsive to existing therapies than the other forms of melanoma because it is more likely to be diagnosed at a later stage, when it has had time to spread. While ALM is rare, it is the most common form of melanoma in people of color. The legendary reggae musician Bob Marley died of ALM in 1981 at the age of 36 when a spot under his toenail that he believed was caused by a soccer injury turned out to be cancerous. (3)
Nodular Melanoma
The most aggressive of all melanoma skin cancers, this invasive form penetrates deep into the skin and accounts for 10 to 15 percent of all cases. Nodular melanoma usually appears on the back, chest, legs, or arms of elderly people, or on the scalp of men. It generally looks like a black bump but may also be blue, gray, white, brown, tan, red, or skin tone. (1) This type of melanoma may also present as an ulcerating or bleeding lesion. There are also two other very rare types of melanoma:
Ocular Melanoma
Ocular (eye) melanoma accounts for less than 4 percent of all melanomas. Most melanomas of the eye develop in the uvea — the middle layer of the eyeball. Caucasians are at much higher risk for this cancer than people of color. Having light-colored eyes is another risk factor. While people can develop eye melanoma at any age, incidence increases with age. Men are slightly more likely to have this melanoma than women. Certain inherited conditions seem to raise the risk as well. People with many abnormal moles on their skin, a condition called dysplastic nevus syndrome, are at greater risk for both melanoma of the skin and of the eye. People with abnormal brown spots on the uvea also fall into a higher-risk group. While research has established an incontrovertible link between exposure to ultraviolet (UV) rays and melanoma of the skin, scientists have not been able to prove conclusively that the same is true for eye melanoma. (4) As with other forms of melanoma, early detection is key: When the cancer is confined to the eye, the five-year survival rate is 80 percent. (5) But many people don’t have symptoms until the cancer is more advanced. Be sure to alert your doctor if you notice any of the following:
Blurry vision or sudden vision lossFloaters — spots or squiggles drifting in the field of vision — or flashes of light (note that floaters often develop as a normal part of aging)Losing part of your field of sightA growing dark spot on the colored part of the eye (iris)Change in the size or shape of the pupil.Change in position of the eyeball within its socketEye bulgingShift in the way the eye moves within the socket (6)
Mucosal Melanoma
This is another rare form of melanoma, accounting for about 1 percent of all cases. The cancer develops in the mucosal surfaces of the body lining the sinuses, nasal passages, oral cavity, vulva, vagina, anus, and other internal areas. As with the skin, these tissues contain melanocytes that can become cancerous. Around half of all cases develop in the head and neck regions while a quarter start in the anorectal region and 20 percent begin in the female genital tract. The remainder occurs in the esophagus, gallbladder, bowel, conjunctiva, and urethra. Researchers have not been able to identify any risk factors. Neither UV exposure nor family history seems to play a role. Like other rare forms of melanoma (for example, acral and ocular), mucosal melanoma has a different pattern of cancer-driving mutations. Most cases of mucosal melanoma are already fairly advanced at the time of diagnosis, leading to a poor prognosis. (7)
