Skin cancer is the most common form of cancer in the United States. One in every five U.S. adults will develop some type of skin cancer during their lives—more than breast, colon, prostate, and lung cancer combined. The three major types are basal cell, squamous cell, and melanoma, in decreasing order of frequency. Melanoma accounts for around 1 percent of all skin cancer cases, but advanced melanoma causes the majority (75 percent) of skin cancer deaths.
Melanoma can arise anywhere on the body, including areas never exposed to the sun, but it typically affects the upper back, chest, arms or legs. Melanoma can also occur when a benign (noncancerous) mole becomes malignant.
What is melanoma?
Melanoma begins in pigment-producing skin cells called melanocytes. “With sun exposure, the cells make melanin, a dark pigment that causes us to tan. Melanin shields melanocytes and other skin cells from the sun’s rays,” explains Robert M. Conry, M.D., associate professor of hematology and oncology, University of Alabama at Birmingham. “When a melanocyte forms a tumor, it’s called a melanoma.”
Melanoma occurs in four basic types:
1. Superficial spreading melanoma, the most common (70 percent of cases), is typically found in young people and usually occurs on the trunk, legs and upper back.
2. Lentigo maligna arises on chronically sun-exposed skin, typically in elderly patients.
3. Acral lentiginous appears on the soles of the feet or the palms; it is most common in dark-skinned people.
4. Nodular melanoma, which is the most severe, is more deeply invasive at the time of diagnosis, and mostly affects older people.
Melanoma is grouped into stages that indicate how far it has spread. “Staging consists of three different pieces of information,” explains Isabella C. Glitza Oliva, M.D., Ph.D., assistant professor of melanoma medical oncology at the University of Texas MD Anderson Cancer Center in Houston. “These include the thickness of the primary melanoma, whether lymph nodes are involved, and whether it has spread further, potentially to other organs.” These and other descriptive features are commonly known as the TNM staging system (for tumor, nodes and metastasis).
TNM stages 0 and I are superficial, stage II is an intermediate stage, and stages III and IV are considered advanced, with cancer spread to lymph nodes or other organs.
Who gets melanoma?
Melanoma can occur at any age. Before age 50, women have a higher risk of melanoma, while at 50 and older, men have a higher risk.
The American Cancer Society estimates that about 76,000 Americans will be diagnosed with melanoma in 2016, and more than 10,000 people will die of it this year. The good news: About 98 percent of melanomas can be cured when detected early.
Causes and risk factors
About 90 percent of all skin cancers are caused by ultraviolet (UV) radiation exposure from the sun. Having more than five sunburns during childhood doubles the risk of melanoma.
Another common cause is the use of indoor tanning beds. “Studies have shown that as few as three episodes of UV tanning can create a 40 percent increase in the incidence of melanoma, and the more times people use tanning beds, the greater their risk,” Conry says. “Melanoma has been substantially increasing in incidence over the last 30 years.”
Melanoma does not spring up overnight, however. “There’s a latency period of anywhere from 10 years to 50 years from when you got the sun exposure to when you clinically develop melanoma,” Conry says.
Risk factors include fair skin, number of moles, personal history of non-melanoma skin cancer, family history of melanoma and a weakened immune system. Dark-skinned individuals have the lowest risk but are more likely to have advanced melanoma by the time it is detected.
Fortunately, the outlook for those with melanoma has never been better. Treatment options have multiplied during the past decade, with many newly approved and experimental treatments that are making a striking difference in improving outcomes for patients with advanced melanoma.