Because it often goes undetected, and can metastasize to other organs and areas of the body, melanoma is the most dangerous of skin cancers. Though not the most common skin cancer (it accounts for only about five percent of skin cancer cases), melanoma does cause the most deaths. The John Wayne Cancer Institute (JWCI) reports the alarming statistics: “While most cases [of melanoma] are discovered early when cure is likely, about 30 percent of patients will die of the disease.” Cases in the United States have been growing in recent decades, with an estimated 68, 130 new cases reported in 2010, according to the American Cancer Society (ACS).
Your skin is not simply a protective shell or covering, like a blanket. It is the largest organ in your body, and serves a variety of essential functions such as protecting other organs, warding off germs, controlling body temperature, and guarding you from harmful ultraviolet (UV) rays.
There are three layers of the skin:
- epidermis: top layer, which protects the other layers and the organs
- dermis: middle layer
- subcutaneous tissue: bottom layer
If you were to examine a cross-section of the epidermis, you would see layers, tiered like a slice of cake, with the topmost layer protecting the other layers and the organs, and the bottom one made up of basal cells.
The outermost layer sheds dead cells, which get replaced by new ones. Here, too, is another type of cell, melanocyte, responsible for producing the brown pigment, melanin. It’s melanin that gives skin a tan or brown color and protects the skin from the sun. Melanocytes, however, can develop into melanoma.
Melanoma can appear on normal skin, or it may form on an existing mole or other area that has changed in appearance. Some moles, present at birth, can develop into melanoma as well. If the melanoma is detected early, before the tumor has the chance to spread, it is much more likely to be cured.
According to the National Cancer Institute, “the three major types of skin cancer are the highly curable basal cell carcinoma, squamous cell carcinomas and the more serious malignant melanoma.” Melanoma can further be divided into categories.
The four major types of melanoma include:
- Superficial spreading melanoma: The most common type, accounting for about 70-75 percent of cases, according to the American Melanoma Foundation (AMF). Usually flat and irregular in shape and color, this form appears in different shades of black, brown, and purple, and is most common among Caucasians.
- Nodular melanoma: This type typically starts as a raised area, in dark blackish-blue or bluish red (although some have no color) with irregular borders, and is more common among men.
- Lentigo maligna melanoma: This type usually appears in the elderly as sun-damaged skin on the face, neck, and arms; it shows up as a pigmented lesion that grows over time into flat areas ranging in color from tan to dark brown or black. According to the AMF, it is “three times more common in females.”
- Acral lentiginous melanoma: The least common form, it usually appears on the palms, soles of the feet, and under the nails, and is more common in African Americans.
Melanoma starts in the melanocytes, which are located in the layer of basal cells found in the deepest part of the epidermis. Though typically of a brown or black color, melanoma can also be tan, pink, or white. Melanoma usually appears first on the chest or back in men, and on the legs in women.
Written by: the Healthline Editorial Team
Medically reviewed by Jennifer Monti, MD, MPH