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, 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.
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.
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.
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.
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:
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.
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:
Young children are an exception to the survival rates for adults. For reasons not fully understood, survival in children is more closely related to age than to the thickness of the cancer, with younger children being less likely to survive than older children or teenagers.
A family doctor can often spot suspicious-looking changes in a patient's skin, but will usually refer the patient to a dermatologist (DER-muh-TAWL-oh-jist) for a definite diagnosis. Dermatologists are doctors with specialized training in diagnosing and treating skin disorders.
To diagnose cutaneous melanoma, a dermatologist first uses a dermatoscope, which is a special palm-sized instrument with a magnifying lens and built-in light. The use of dermatoscopes has increased the accuracy of diagnosing malignant melanoma by 20 percent, because the doctor can make digital images of suspicious moles or skin areas and save them for comparison with images from later checkups.
If the dermatoscope images suggest that the patient may have melanoma, the next step is to take a sample of the abnormal mole or area of skin to be sent to a laboratory for analysis under a microscope. This procedure is called a biopsy (BI-op-see). In the case of melanoma, the doctor removes the entire mole rather than just a portion of it to obtain an accurate measurement of Breslow's depth. Biopsies are done under local anesthesia * .
To evaluate whether the melanoma may have spread beyond the skin, the doctor may perform a sentinel lymph node biopsy. A sentinel lymph node is the lymph node closest to the melanoma, the one to which the cancer is most likely to spread.
There was no blood test as of 2016 that could detect malignant melanoma.
The only definite cure for malignant melanoma is surgical removal of the cancerous mole or patch of skin before the melanoma reaches a Breslow's depth of 1 millimeter. The surgeon removes a margin of normal skin surrounding the melanoma as well as the tumor itself to make sure that no cancerous cells are left behind.
Patients with later-stage melanomas are treated with surgery to remove cancerous lymph nodes. Surgery by itself is not effective in treating melanoma that has spread to other organs. In these cases, a combination of chemotherapy * , radiation therapy *
People cannot change certain risk factors for melanoma, such as their genes or basic skin type, but they can lower their risk of melanoma by taking care of their skin. One way is to be careful about sun exposure. Some specific strategies are as follows:
Another important way to lower one's risk of malignant melanoma is regular self-examination of the skin. The American Academy of Dermatology outlines the steps to take:
Because slightly more than half of melanomas do not start in moles, doctors do not think that removing normal moles in teenagers or young adults is a useful way to prevent melanoma.
Vaccines for melanomas have been undergoing clinical trials as biological therapies for patients with stage 2 or stage 3 melanoma, but the results will take several years to evaluate. There was no vaccine as of 2016 to prevent melanoma; however, the Food and Drug Administration (FDA) did approve a vaccine called T-VEC or Imlygic® to treat some patients with metastatic melanoma that cannot be removed by surgery.
See also Cancer: Overview • Skin Cancer
Habif, Thomas P. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Philadelphia, PA: Saunders, 2015.
National Comprehensive Cancer Network. NCCN Guidelines for Patients: Melanoma. Fort Washington, PA: National Comprehensive Cancer Network, 2014.
University of Gothenburg. “Antioxidants Cause Malignant Melanoma to Metastasize Faster.” ScienceDaily. October 8, 2015. http://www.sciencedaily.com/releases/2015/10/151008131112.htm (accessed March 3, 2016).
Zager, Jonathan S., Vernon K. Sondak, and Ragini Kudchadkar, editors. Melanoma. Oxford, UK: Oxford University Press, 2016.
American Cancer Society. “Skin Cancer – Melanoma.” http://www.cancer.org/cancer/skincancer-melanoma/index?cancerTypeRedirect=/Cancer/index (accessed March 3, 2016).
Health Guide. “Melanoma.” The New York Times. http://www.nytimes.com/health/guides/disease/melanoma/overview.html (accessed March 3, 2016).
National Cancer Institute. “Cancer Vaccines.” http://www.cancer.gov/about-cancer/causes-prevention/vaccines-fact-sheet (accessed March 3, 2016).
Skin Cancer Foundation. “Melanoma.” http://www.skincancer.org/skin-cancer-information/melanoma (accessed March 3, 2016).
American Academy of Dermatology. PO Box 4014, Schaumburg, IL 60168. Toll-free: 866-503-7546. Website: https://www.aad.org (accessed March 3, 2016).
American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: http://www.cancer.org (accessed March 3, 2016).
Melanoma Research Foundation. 1411 K St., NW, Suite 800, Washington, DC 20005. Toll-free: 800-673-1290. Website: http://www.melanoma.org (accessed March 3, 2016).
National Cancer Institute. BG 9609 MSC 9760, 9609 Medical Center Dr., Bethesda, MD 20892. Toll-free: 800-422-6237. Website: http://www.cancer.gov (accessed March 3, 2016).
Skin Cancer Foundation. 149 Madison Ave., Suite 901 New York, NY 10016. Telephone: 212-725-5176. Website: http://www.skincancer.org (accessed March 3, 2016).
* malignant (ma-LIG-nant) refers to a condition that is severe and progressively worsening.
* cutaneous (kyoo-TAY-nee-us) means related to or affecting the skin.
* ultraviolet is a wavelength of light beyond visible light; on the spectrum of light, it falls between the violet end of visible light and x-rays.
* DNA or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik AH-sid) is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
* mutations (mu-TAY-shuns) are changes in an organism's gene or genes.
* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
* chromosomes (KRO-mo-somz) are threadlike chemical structures inside cells on which the genes are located. There are 46 (23 pairs) chromosomes in normal human cells. Genes on the X and Y chromosomes (known as the sex chromosomes) help determine whether a person is male or female. Females have two X chromosomes; males have one X and one Y chromosome.
* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* local anesthesia (an-es-THEEzha) means using medicine to block or numb pain in one part of the body while the patient remains awake. General anesthesia blocks pain over the entire body while the patient sleeps.
* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.
* radiation therapy is a treatment that uses high-energy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths.