Malignant Melanoma

Malignant * melanoma is a skin cancer that originates in the pigment-producing cells in the upper layer of the skin known as melanocytes (me-LAN-oh-sites). Malignant melanoma is one of the less common types of skin cancer, but it causes the highest number of deaths, accounting for 75 percent of all deaths resulting from skin cancer, and it accounts for 6 percent of cancer cases in teens 15 to 19 years old. Most melanomas begin in the skin, but some begin in the eye or even the intestines. Melanoma that starts in the skin is called cutaneous * melanoma. Melanoma that starts in the eye is called uveal (YOU-vee-ul) or ocular melanoma.

John's Story

John, a high school senior, lives for baseball season, when he spends hours each day practicing with teammates as well as playing games against teams from other schools. His chief concerns with health matters are drinking enough water in hot weather and not overworking his pitching arm. He was surprised when the coach told him and his teammates before the start of spring training that they would have to be more careful about protecting their skin from the sun. The coach had read a bulletin from the American College of Sports Medicine about the dangers to young athletes from too much sun exposure, particularly the risk of melanoma. John had never thought of sunlight as harmful to his skin. He has always enjoyed hiking in the mountains of the Southwest as well as sports and other outdoor activities. He is also three-fourths Native American and does not sunburn as easily as some of his lighter-skinned teammates. But the coach told John that people from any racial or ethnic group can get melanoma if they have a history of it in their family; live in-regions like northern New Mexico or Arizona; or have had occasional severe sunburns in childhood. The coach also said that as recently as the early 1990s, doctors rarely saw teenagers with melanoma, but that more and more cases were being found among young people John's age. John decided that he would ask his doctor to recommend an effective sunscreen for his skin type; and that he would always be careful to wear a baseball cap and shirt during practice, because boys are more likely than girls to develop melanomas on the head, neck, and chest.




A cutaneous pigmented lesion that had been diagnosed as superficial spreading malignant melanoma (SSMM).





A cutaneous pigmented lesion that had been diagnosed as superficial spreading malignant melanoma (SSMM).
CDC/Dr. Carl Washington and Dr. Mona Saraiya.

What Is Malignant Melanoma?

Malignant melanoma is a type of skin cancer that begins in certain cells in the epidermis (eh-pih-DER-miss), which is the outermost layer of the skin. These specialized cells are called melanocytes because they produce and contain a brownish-black skin pigment called melanin (MELL-uhnin). In humans, melanin provides the color in the skin, hair, and the colored part of the eye called the iris. There are between 1,000 and 2,000 melanocytes in each square millimeter of skin. The difference in skin color between fair-skinned and darker-skinned people does not depend on the number of melanocytes in the skin but on their level of activity. When skin is exposed to the sun, the melanocytes become more active, produce more melanin, and cause the skin to darken; that is, they cause a suntan.

The development of melanomas from normal skin was not completely understood as of 2016. Some researchers believe there may be several different pathways to melanoma, depending on whether they occur on skin that is exposed to the sun only occasionally (such as the chest or back area in women) or on skin that is frequently exposed to the sun (head, face, neck, and hands). In general, melanoma is caused by the interaction of ultraviolet * (UV) radiation from the sun and the melanin in melanocytes. UV radiation can damage the DNA * in skin cells both directly and indirectly. Researchers have found that 92 percent of melanomas are caused by indirect damage to DNA and 8 percent by direct damage.

When the DNA in a skin cell is damaged by UV radiation, the cell can undergo a series of mutations * that lead to abnormal multiplication of new cells. In some cases, the changed DNA makes the cells more vulnerable to the damaging effects of UV radiation. About 40 percent of melanomas begin in moles, with the remaining 60 percent starting in normal-looking skin.

Melanomas grow in two stages or phases. The first is a phase of outward or radial growth. The second phase, which is much more dangerous, is a phase of vertical growth into deeper layers of tissue. It is during this second phase of growth that melanomas become harder to treat and able to spread to other parts of the body.

How Common Is Malignant Melanoma?

Malignant melanoma was considered a rare form of cancer until the 1970s, but its rate among Caucasians in the United States tripled between 1985 and the early 2000s. It was the sixth most common cancer for both men and women as of 2016. As of 2016, the lifetime risk of developing invasive melanoma was 1 case for every 50 Americans, a 2,000 percent increase since 1930. This risk rises to 1 case for every 33 Americans if early-stage melanoma (stage 0 below) is included. About 9,900 people died of melanoma in the United States in 2015.

MELANOMA AND ENVIRONMENTAL FACTORS

Melanoma was a rare form of cancer until the 20th century. The earliest known surgical removal of a melanoma was performed in 1787 by a British surgeon, but the disease was little studied until the 1840s and 1850s, when two other British doctors described the stages of melanoma and found that it runs in some families. The connection between melanoma and sun exposure was not made until 1956, when Australian physician Henry Lancaster (1913–2001) found that high intensity of sunlight is a risk factor for melanoma. In the 1970s, scientists began to notice that the ozone layer—a layer of oxygen molecules consisting of three atoms of oxygen in the upper atmosphere—was becoming thinner. The ozone layer helps to block a high-energy type of ultraviolet radiation known as UVB from reaching the earth's surface, so doctors began to wonder whether a thinner ozone layer could contribute to an increase in the rate of melanoma and other skin cancers.

Doctors do not think that the rise in cases of melanoma since the 1980s was due primarily to changes in the ozone layer. One reason is that depletion of the ozone layer is most severe over Antarctica, which is not a heavily populated continent. Another is that advances in genetics indicate that heredity plays a larger role in melanoma than was thought to be the case in the 1980s. Still another reason for skepticism about the role of the ozone layer in melanoma is that some studies indicated that a lower-energy form of ultraviolet radiation called UVA triggers the development of melanoma rather than the UVB blocked by the ozone layer. If this finding is accurate, then changes in the ozone layer are not related to melanoma. It is also likely that the increase in the number of reported cases of melanoma since the 1990s is due partly to better diagnostic instruments and earlier diagnosis.

Research into the rise in cases of melanoma has been ongoing in the United States. According to a report published by the Department of Health and Human Services, the Climate Change Science Program will include studies on the effect of UVA and UVB radiation on the skin; research into the effectiveness of various sunscreen products; and studies of the role of genes in triggering melanoma and other skin cancers.

The highest annual rates of melanoma in the world are found in Australia, New Zealand, and Israel. There were approximately 34.9 cases of melanoma annually per 100,000 people in Australia as of 2012, and 40 cases annually per 100,000 people each year in Israel.

One unusual finding in the United States is the rapid increase of deaths from melanoma in older males. The death rate among younger men (44 years or younger) from melanoma has dropped, most likely as a result of public health education campaigns about the dangers of sun exposure. The majority of people diagnosed with melanoma are Caucasian men over age 50. Caucasian men over age 65 have had a 5.1 percent annual increase in melanoma incidence since 1975, the highest annual increase of either sex or any age group.

Who Gets Malignant Melanoma?

Genetic * factors are involved in malignant melanoma, in part because skin color and sensitivity to the sun are inherited characteristics. In addition, melanoma is known to run in some families. Researchers have identified mutations in certain genes on chromosomes * 1, 9, and 12 in families with histories of malignant melanoma.

Melanoma is more common in women than men up to age 40; however, in adults over 40, it is more common in men. The average age of Americans at the time of diagnosis of melanoma is 53 years, but it is the most common cancer in women between the ages of 25 and 29 and is second only to breast cancer in women between the ages of 30 and 34. In terms of racial groups in the United States, melanoma affects Caucasians 20 times more often than African Americans and 6 times more often than Hispanics.

The parts of the body where melanoma is most likely to start differ somewhat between men and women and between African Americans or Asians and members of other races. Men are more likely to develop melanoma on the head, neck, or chest; women, on the lower legs. African Americans and Asians are more likely to get melanoma under the nails or on the palms of the hands and soles of the feet.

There are other factors that increase the risk of melanoma. These include the following:

How Is Malignant Melanoma Diagnosed?

About 80 percent of melanomas and other skin cancers are found by patients who notice suspicious changes in their skin and go to their doctor. The signs of melanoma are sometimes called the ABCDEs. A mole or patch of skin developing into melanoma may have the following features:

Early-stage melanomas may itch or shed small flakes of skin, whereas more advanced melanomas may bleed or ooze fluid as well as itch. Advanced melanomas may also become hard or lumpy in texture. Melanomas do not usually cause pain.

How Serious Is Malignant Melanoma?

Malignant melanoma is the deadliest form of skin cancer. As noted earlier, melanoma accounts for only 4 percent of skin cancers in the United States, but it is responsible for 75 percent of deaths from skin cancer. An estimated 9,940 people will die of melanoma each year in the United States. According to the World Health Organization, 132,000 melanoma skin cancers occur globally each year.

Malignant melanoma is curable if caught early. When a melanoma is not removed in its early stages, cancer cells will start to grow downward from the skin surface and invade healthy tissue. The disease can then spread to other parts of the body where it is difficult to control. Measuring a cancer's size, thickness, and likelihood of spreading is called staging. Melanomas are graded in five stages from 0 to 4. The chief factor in determining a patient's chances of recovery is the thickness of the melanoma. This is measured in millimeters and is called Breslow's depth, after the doctor who first connected it to the patient's chances of survival in 1970.

The five stages of melanoma and a person's chances of five-year survival at each stage are as follows: