An Introduction to Melanoma
Melanoma is the most serious type of cancer affecting the skin. Each year in the United States, more than 53,600 people learn that they have melanoma. In some parts of the world, especially among Western countries, melanoma is becoming more common every year. In the United States, for example, the percentage of people who develop melanoma has more than doubled in the past 30 years.
Melanoma is one of the most serious types of
skin cancer because advanced melanomas have the ability to spread to other parts of the body. When melanoma starts in the skin, the disease is called cutaneous melanoma. It can also develop in the eye (called
intraocular melanoma) or in other parts of the body where pigment cells are found. In rare cases, melanoma may arise in the meninges, the digestive tract, lymph nodes, or other areas where melanocytes are found. Melanomas that begin in areas other than the skin are not discussed in this article.
Melanoma: Understanding the Skin
The skin is the body's largest organ. The skin:
- Protects against heat, sunlight, injury, and infection
- Helps control body temperature
- Stores water, fat, and vitamin D.
The skin has several layers, but the two main layers are the epidermis (the upper or outer layer) and the dermis (the lower or inner layer).
Skin cancer begins in the epidermis, which is made up of three kinds of cells:
- Squamous cells: Thin, flat cells that form the top layer of the epidermis.
- Basal cells: Round cells under the squamous cells.
- Melanocytes: Found in the lower part of the epidermis, these cells make melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment, causing the skin to tan, or darken.
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