Melanoma is the most aggressive type of skin cancer. About 76,690 people will be diagnosed with melanoma skin cancer in the U.S. in 2013, and roughly 9,480 will die from it. While melanoma accounts for less than 5% of all skin cancers, it is responsible for a large majority of skin cancer deaths. Melanoma is one of the more common cancers in young adults — particularly young women — and is not uncommon in those under 30. Melanoma rates have been increasing for the last 30 years, and are highest among people in their 80s.
What is Melanoma?
Different skin cancers start in different layers or cells of the skin. Cells located in the basal layer of the epidermis, called melanocytes, produce a brown-black skin pigment (melanin) that determines skin and hair color. Melanin also helps protect the skin against the damaging rays of the sun.
As a person ages, melanocytes often increase in number, forming concentrated clusters that appear on the surface as small, dark, flat, or dome-shaped spots. When this cell proliferation occurs in a controlled manner, the resulting lesion is benign (non-cancerous) and is commonly referred to as a mole or nevus. Sometimes, however, pigment cells grow out of control and become a cancerous and life-threatening melanoma.
At first, melanoma cells are found in the epidermis and top layers of the dermis. However, once they grow downward into the dermis, the cancer can come into contact with lymph and blood vessels. The thicker the melanoma, the greater the likelihood that it could spread to distant sites. Removal of the lesion before it reaches the deeper layers of the skin is important for achieving a cure.
Types of Melanoma
Superficial Spreading Melanoma. Superficial spreading melanoma is the most common melanoma skin cancer — and the most curable. It is flat, asymmetrical, unevenly colored, and usually grows outward across the surface of the skin.
Nodular Melanoma. Nodular melanoma skin cancer appears as a fast-growing brown or black lump, and its characteristics do not always fit the definitions described above.
Lentigo Maligna. Lentigo maligna (sometimes called Hutchinson's freckle) usually occurs in elderly people and is marked by flat, mottled, tan-to-brown freckle-like spots with irregular borders. These lesions often appear on the face or other sun-exposed areas and can take 5-15 years before they become invasive, after which the condition is called "lentigo maligna melanoma."
Acral Lentiginous Melanoma. Although rare, acral lentiginous melanoma skin cancer is the most common melanoma among African and Asian populations. It commonly appears as a dark patch on the palms, soles, fingers, toes, under fingernails or toenails, or in mucous membranes.
Amelanotic Melanoma. A rare melanoma that can be very hard to diagnose because it is pink or flesh-colored. It also breaks the general "ABCDE" rule for recognizing most melanomas.
If untreated, melanoma cells usually spread first through the lymph vessels or glands. Melanoma cells can also spread by way of blood vessels to various organs, spreading cancer to the liver, lungs, brain, or other sites.
Melanoma skin cancer tends to grow in stages. At first, most melanomas tend to be flat initially and spread laterally across the skin surface as they grow. At this early stage, which can last 1 to 5 years or longer, removal of the growth has an excellent chance of curing the melanoma. Still, there is a chance that some of these melanomas are invasive, and they should be treated aggressively. Lesions that become raised or dome-shaped over at least part of their surface indicate that downward growth has occurred. In some cases, this growth is rapid, occurring over a period of weeks to months. Later-stage melanoma is difficult to treat, especially when it has metastasized to distant organs or lymph nodes.
Any suspicious lesion should be checked immediately (this photo gallery shows what they look like), particularly if it has grown quickly or is partially flat and partially raised.
Common sites of melanoma skin cancer in men include the head, middle of the body (trunk), and neck. In women, common sites are the arms and legs. However, any area of the skin may be affected. You may not notice melanomas if they appear on areas that are difficult to examine, such as the scalp or the back. Less common sites for melanoma include:
- Soles of the feet
- Under the fingernails or toenails
The presence of a dark lesion under the nail that runs into the adjoining skin and doesn't heal may signal melanoma. Rarely, melanomas appear in the mouth, in the iris of the eye, or in the retina at the back of the eye, where they may be detected during dental or eye examinations.
More Melanoma Information
- Melanoma skin cancer pictures pictures
- The stages of melanoma
- Treatment of early-stage melanoma
- Treatment of advanced melanoma
- Reduce your risk of melanoma by avoiding tanning salons
"What Are the Key Statistics About Melanoma?" American Cancer Society. May 2013. 30 May 2013.