What are melanomas?

Related conditions:
Basal cell cancer, squamous cell cancer

Definition:

Melanomas are malignant tumors of the skin that occur in the melanocytes, the cells that produce melanin (skin pigment).

Risk factors: Melanomas occur most commonly in fair-skinned people, particularly natural blonds and redheads, especially those with a history of sun exposure or multiple serious sunburns. A history of serious sunburns in childhood is a particular risk. Risk for the disease is strongly related to having a family history; which is characteristic of about 1 in 10 of patients with melanoma. Additional risk factors include large or multiple moles and past personal history of melanoma or of less serious skin cancers, known as basal cell or squamous cell cancers. People with diseases that suppress the immune system are at added risk for melanoma. Occupational exposure to coal tar, pitch, creosote, arsenic compounds, or radium increase a person’s risk for the disease. Celtic descent, male gender, and older age are also risk factors.

Etiology and the disease process: Repeat exposure to harmful ultraviolet rays from the sun or artificial sources such as sunlamps or tanning booths appears to be the most significant factor contributing to the development of melanoma. This is borne out by the fact that the incidence of melanoma increases in the lower latitudes of the world where the sun is strongest. Additionally, in parts of the world where the ozone layer is thin, the incidence is higher. In Queensland, Australia, for example, where there is a hole in the ozone, between 1979 to 1987, the rate of melanoma doubled to 55.8 per 100,000 men and rose to 42.9 per 100,000 women.

Melanomas can occur on parts of the body not usually exposed to the sun, including the soles of the feet and the genitals. Melanoma starts with an abnormal skin growth, which is generally quite small. When discovered at this early stage, melanomas can be easily removed and the cancer cured. If the growth is not removed, it thickens and invades surrounding tissue and nearby lymph nodes. The cancer can then spread through the lymph nodes to sites distant from the original growth, including vital organs, soft tissues, and other lymph nodes.

Incidence: In the 1970s, the incidence rate of melanoma rose dramatically to about 6 percent a year. Incidence continues to rise but at a slower rate; from 1981 to 2001 the rate of growth was about 3 percent a year. In 2011, the number of new cases of melanoma was 21.3 per 100,000 men and women.

Melanoma affects adults of all ages as well as teenagers. According to the American Cancer Society, an estimated 76,100 new melanomas would be diagnosed in 2014, with about 9,710 deaths from melanoma. Rates for whites are ten times higher than for African Americans. However, one type of melanoma, which develops on the palms of the hands, soles of the feet, and nail beds, occurs more frequently in African Americans and Asians.

Symptoms: Melanoma generally first appears as a new mole or a change in the shape, size, or color of an existing mole. The American Cancer Society describes the warning signals in terms of a mnemonic: ABCD. “A” for asymmetry, meaning that the mole is not uniformly round; “B” for border, in that the edges of the mole are irregular; “C” for color, referring to the varied colors (generally in tones of tan, brown, and black) throughout the mole; and “D” for diameter, meaning that the mole is larger than 6 millimeters (mm).

Screening and diagnosis: People with serious risk factors or symptoms should have regular full body exams by a dermatologist to identify any skin abnormalities, and baseline photographs should be taken so that any changes can be tracked. Suspect moles or skin abnormalities should be removed and analyzed for cancer cells.

The stages of melanoma are defined as follows:

• Localized, Stage 0: These melanomas involve only the top layer of skin, the epidermis.





• Localized, Stages I and II: These melanomas involve the underlying layer of skin, the dermis, and are rated according to the depth they penetrate the skin (known as the Breslow depth) and their degree of ulceration (how much the epidermis is eroded and exposes the dermis below). Ulceration is determined by a pathologist, using a microscope.





• Regional, Stage III: These melanomas include those in which the cancer has spread to nearby lymph nodes.





• Advanced, Stage IV: These melanomas include those where cancer has spread beyond the region of the skin growth to distant sites in the body, including internal organs and distant lymph nodes.

Treatment and therapy: Significant advances have been made in the early detection of melanoma. All suspect moles or skin growths should be removed and tested for cancerous cells. Removal of localized growths (Stages 0-II) can be done one of three ways: surgically, cutting out the suspect tissue; by electrodessication and curettage, using an electric current to destroy the tissue and then scraping the area with a special tool to remove any possible remaining cancer cells; or by cryosurgery, which freezes the tissue. About 83 percent of melanomas are diagnosed in these early stages while the cancer is still confined to the primary skin growth, according to the Duke Raleigh Hospital Cancer Center. Surgery successfully removes the cancer for the majority of patients with early-stage melanoma. In some cases, radiation therapy may be directed at the area following surgery to kill any cancer cells that may remain. Patients with Stages 0 to II melanoma have an excellent prognosis.

If the growth is extensive, the surgeon will remove lymph nodes to determine if the cancer has spread. After their removal, Stage III and IV melanomas may be treated with radiation or immunotherapy (agents that attempt to harness the human body’s own disease-fighting properties to kill cancer cells) or chemotherapy (toxic agents targeted to kill cancer cells). Two therapeutic agents approved by the US Food and Drug Administration (FDA) for the treatment of Stage III and IV melanoma are dacarbazine (DTIC, chemotherapy) and interleukin-2 (IL-2, immunotherapy). Some patients with Stage III and IV disease experience a full recovery with chemotherapy; however, positive responses to the drug therapy, when they occur, are most often partial and brief. Much research is being done to explore other possible treatments for melanoma, including combinations of different chemotherapies and new immunotherapies. Some of these agents are not specifically approved by the FDA to treat melanoma. Patients with melanoma may be eligible to become subjects in clinical trials in which these experimental agents or combinations of agents are tested.

Prognosis, prevention, and outcomes: The thickness of a patient’s tumor is the best single indicator of the prognosis. After having melanomas of less than 0.76 mm removed, about 96 to 99 percent of patients are cured. About 1 in 10 patients with melanoma is diagnosed after the cancer has already spread to nearby lymph nodes. For these patients in the regional stage (Stage III), the prognosis is not as good, but survival rates for patients with Stage III disease range widely, depending on how many lymph nodes are affected by the cancer. About 3 of 10 patients with melanoma are diagnosed in an advanced stage (Stage IV), after the cancer has already spread (metastasized) to distant sites. Those with metastases to the skin or soft tissue or to distant lymph nodes appear to fare better than those with lung or other vital organ metastases.

Recommended measures to prevent melanoma include avoiding excessive direct sunshine, especially during the hours when the sun is high in the sky (from about 10 a.m. to 2 p.m.); using sunscreen and protective clothing to prevent sunburn; and not using sunlamps; tanning booths, or other artificial sources of ultraviolet light. People should become familiar with the moles and spots on their bodies and report any changes that could indicate melanoma to their doctors.

Bolognia, Jean, Julie V. Schaffer, Karynne O. Duncan, and Christine J. Ko, eds. Dermatology Essentials. Oxford: Saunders/Elsevier, 2014. Print.

Gershenwald, Jeffrey E. Melanoma. Philadelphia: Saunders, 2011. Print.

Kaufman, Howard. The Melanoma Book: A Complete Guide to Prevention and Treatment. New York: Gotham, 2005. Print.

Poole, Catherine M., and I. V. DuPont Guerry. Melanoma: Prevention, Detection, and Treatment. 2d ed. New Haven: Yale UP, 2005. Print.

Schofield, Jill R., and William A. Robinson. What You Really Need to Know About Moles and Melanoma. Baltimore: Johns Hopkins UP, 2000. Print.

Sharfman, William. Melanoma. New York: Demos Medical, 2012. Print.