A malignant melanoma is the most severe type of skin cancer, characterized by invasive, abnormal skin cell growth that can easily spread throughout the body. There are four different subtypes of malignant melanoma, as well as a rare congenital disease that can lead to a melanoma. While each of these examples differs in its presentation and course of development, each is considered very serious and requires prompt medical treatment.
Superficial Spreading Melanoma
Approximately 70 percent of all malignant melanomas are superficial spreading melanomas, according to the Cleveland Clinic. These melanomas often develop from pre-existing moles and are very common among fair-skinned individuals. Areas of skin exposed to the sun are most commonly affected, particularly the upper back and lower legs.
According to the American Melanoma Foundation, superficial spreading melanomas usually occur in men and women who are in their 50s, although they can occur among all age groups. For a long period of time, these lesions grow horizontally across the skin. They often appear as elevated areas of unevenly pigmented skin that can be brown, black, grey, white, purple, pink or blue in pigmentation. The moles exhibit classically irregularly shaped borders and, over time, may develop focal spots that darken in color. After growing horizontally, they become invasive, spreading downward into the skin.
Nodular Melanoma
According to the MD Anderson Cancer Center, nodular melanomas account for between 15 percent and 30 percent of all cases and are the second most common type of melanoma. Nodular melanomas usually develop on the head, neck or trunk, starting off as skin-colored, blackish-blue or bluish-red nodules and grow rapidly and aggressively. They usually occur among people in their 50s. The American Melanoma Foundation notes that these skin lesions are raised with irregular borders. Sometimes they may be ulcerated and have no pigmentation at all. They usually grow vertically down into the deep skin tissue, metastasizing quickly.
Lentigo Maligna Melanoma
Lentigo maligna melanoma typically develops in the elderly on the skin of the neck, head, nose and cheeks. They are especially common among fair-skinned females. According to the Cleveland Clinic, these are the least common type of melanoma. These lesions form superficially and grow very slowly, taking anywhere from five to 50 years to spread to deeper tissues, according to the American Melanoma Foundation. Lentigo maligna melanomas appear flat with irregular borders. They are usually light or dark brown in color; however, rarely they can be skin-colored.
Acral Lentiginous Melanoma
Acral lentiginous melanoma only accounts for 2 percent to 8 percent of melanoma cases overall; however, it is very common among darker-skinned people, especially those who are of Japanese, African American, Latin American and Native American descent, according to the Cleveland Clinic. These lesions usually develop under the nail beds or on the palms of the hands or soles of the feet. Initially, they are flat and smooth with irregular pigmentation and borders; however, they progress quickly into raised moles or nodules. Soon after, they rapidly expand vertically and metastasize throughout the body, according to the American Melanoma Foundation.
Giant Congenital Nevus
Some infants are born with a darkly pigmented patch of skin called a congenital nevus that arises as a result of problems that occurred during pregnancy or genetic defects. According to Medline Plus, the affected area of skin is usually blue-black in color with irregular borders and often contains hair. Sometimes, these nevi continue to grow after childbirth, reaching up to 8 inches in diameter. According to the American Melanoma Foundation, between 2 percent and 40 percent of children with this growth--called a giant congenital nevus--will develop a malignant melanoma.
