People with melanoma, a serious form of skin cancer, now have more hope for survival and more treatment choices than ever before. Doctors keep finding new treatments for melanoma and ways to help people with melanoma lead better lives. We are continually learning more about melanoma and its prevention, detection, and treatment.
What Is Skin Cancer?
There are three types of skin cancer:
Basal cell carcinoma
Squamous cell carcinoma
The most serious skin cancer is melanoma. Melanoma is a much less common form of skin cancer than either basal cell carcinoma or squamous cell carcinoma. It is estimated that about half of all Americans will develop some form of skin cancer at least once in their lifetimes. This section deals with melanoma; see non-melanoma skin cancer for information on basal or squamous cell carcinoma.
What Is Melanoma?
Melanoma is a type of skin cancer that starts in skin cells called melanocytes. Melanocytes are what give skin its color.
Anatomy of the Skin
The skin is the largest organ of the body. Skin protects us from heat, sunlight, injury, and infection. It also stores water and fat, and produces vitamin D. The skin has three layers:
The outer layer, called the epidermis;
The middle layer, called the dermis; and
The inner layer, called the subcutis (the subcutaneous layer in the picture above).
The epidermis is made of flat cells called squamous cells. Round basal cells are under the squamous cells. The lower part of the epidermis also has pigment-producing cells called melanocytes, which darken the skin in response to sun exposure.
The dermis has blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands make sweat, which helps keep the body cool. Other glands make sebum. Sebum helps keep the skin from getting dry. Sweat and sebum reach the skin's surface through tiny openings called pores.
The subcutis and the lowest part of the dermis form a network of collagen and fat cells. This layer conserves heat and helps protect the body's organs from injury.
Normal and Abnormal Moles
Sometimes groups of melanocytes make moles, or nevi. Most people have between 10 and 40 moles on their bodies. These moles are usually pink, tan, or brown. They can be flat or raised, and are usually round or oval. Most moles are on the chest or the upper part of the body.
Moles don't usually grow or change very much. Many times, moles fade in older people. Most moles are benign, or noncancerous, and do not lead to cancer. Some abnormal moles, called dysplastic nevi, pose an increased risk of melanoma and must be examined periodically by a doctor.
Melanoma is the most serious kind of skin cancer. It is believed to begin when normal melanocytes become cancerous. When cancer cells are on the skin, the cancer is called cutaneous melanoma. Most of what we know about melanoma (its behavior, staging, and treatment) refers to cutaneous melanoma.
Melanoma can occur anywhere on the skin. Men usually get it on the part of the body between the shoulders and the hips called the trunk. They may also get it on their head or neck. Women usually get it on their arms and lower legs. Sometimes, melanoma may occur even on areas of the skin that never are exposed to sunlight. It may even occur in the eye or in the nose and sinuses.
If left untreated, melanoma can spread to other parts of the body, such as the liver, lungs, or brain. If melanoma spreads to the liver, for example, the cancer cells in the new tumor are still melanoma cells. The disease is then called metastatic melanoma, not liver cancer.