Melanoma is the sixth most common cancer in the US. It is the deadliest of skin cancers, and causes 8,700 deaths in the US per year. What’s even scarier is that Melanoma rates have been rising increasingly in the past 20 years, so melanoma prevention and medical research is very important.
John Hunter first discovered melanoma in 1787. He described the tumor he found as a “cancerous fungus” and put in the Hunterian Museum in Royal College of Surgeons in England. It wasn’t until 1968 that the tumor was tested and found to be metastasized melanoma. Melanoma was first recognized as an actual disease in 1806, by Rene Laenne. Henry Lancaster made the connection between sunlight intensity and the development of melanoma in 1956.
There are several types of melanoma. The most common type is called Superficial Spreading Melanoma. It usually occurs in Caucasians, and can be found in all body sites. Superficial spreading melanoma produces lesions, usually flat and irregular in shape and color, with different shades of black and brown. Nodular melanoma, which accounts for about 15% of melanoma cases, usually starts as a raised area that is dark blackish-blue or bluish-red. Another type of melanoma is called Lentigo Maligna Melanoma. It is most common in the elderly, and usually occurs in sun damaged skin on the face, neck, arms, hands, soles of the feet, or around the toenails. Lentigo Maligna Melanoma is large, flat, and tan with areas of brown. The least common form of melanoma, Acral Lentiginous Melanoma, usually occurs on the palms, soles, and under the nail. It is more common in African Americans. When melanoma occurs in the colored part of the eye, it is called Melanoma of the Eye, or Ocular Melanoma.
Melanoma is directly linked to sun exposure and ultraviolet radiation. Older people are at a higher risk to develop melanoma, however the disease often affects young, otherwise healthy people. Risk factors include having a fair complexion, living in a sunny climate or at a high altitude, long-term exposure to high levels of strong sunlight, one or more blistering sunburns during childhood, the use of tanning devices, family history of melanoma, being freckle-y or having multiple birthmarks, exposure to certain carcinogens such as arsenic, coal tar, and creosete, and a weakened immune system due to AIDS, leukemia, organ transplants, and various medications.
Melanoma develops when UVA and UVB radiation from sunlight causes certain mutations in the DNA of melanocytes, which are cells that produce melanin, a skin pigment responsible for skin and hair color. These mutations cause errors in the matches of nucleic acids in the DNA strands, specifically the genes involved in cell growth: tumor suppressors and proto-oncognes. When these genes become deformed, they no longer function properly. With mutated tumor suppressors, which are cells that prohibit cell division, and proto-oncognes, which are cells that speed up cell division, cancerous melanocytes virtually have no checkpoint system and divide abnormally fast, producing more cancerous melancytes that then divide and build up and create problems.
The progression of Melanoma is classified into stages. Stage I is classified as Thin Melanoma of the Skin, and happens when cancerous melanocytes begin to accumulate. These atypical melanocytes have mutated genes and produce abnormally large amounts of melanin, causing darker lesions to appear on the skin. These lesions are usually asymmetrical, large, elevated, and have irregular borders and variations in color. When Melanoma is caught in stage I, surgery is done to remove the lesion and patients usually survive, with a 90% survival rate.
Stage II, which is medium or thick melanoma of the skin, is when mutated melanocytes begin to divide radically, causing the cancer to spread deeper into the skin. Surgery is usually used to remove the lesion and surrounding area. Samples of the nearby lymph nodes are also taken to make sure the melanoma has not progressed. There is a 75% survival rate for stage II melanoma.
When the melanoma has progressed to the lymph nodes, or moved a ways from the primary skin lesion, it is classified as stage III. Stage III is harder to treat because the cancer has metastasized, and there is a 30%-60% survival rate depending on the extent of the disease. Treatments include surgical removal of the lesions and affected lymph nodes, radiation, and high-dose interferon-alpha for a year. The interferon boosts the immune system, which helps fight the cancer and prevents it from recurring.
When the melanoma spreads to distant sites in the body, for example organs or multiple lymph nodes, it is classified as stage IV melanoma. Usually, surgery and radiation is used to remove the tumors, and systemic drugs, which are oral or IV drugs that go throughout the body, are administered. Stage IV melanoma has a less than 10% survival rate, and there are no established treatments. Most of the treatments and clinical trials such as interleukin-2, temozolomide, thalidomide, cisplatin-based chemotherapy, and biochemotherapy, which is cisplatin with or without other chemotherapy drugs, combined with interleukin-2 and interferon-alpha. Other experimental treatments and include vaccines, new immunotherapy drugs, anti-angiogenic drugs, molecularly targeted small molecule drugs administered orally or intravenously, and bone marrow transplant from relatives.
These treatments, among many others, are currently being researched to improve the survival rates of melanoma. For the time being, the best way to survive melanoma is to prevent it by wearing sunscreen and watching skin for irregular freckles and moles.
Sources:
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001853
http://www.oncolink.org/types/article.cfm?c=18&s=63&ss=861&id=9623
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