Introduction
Melanoma is the most deadly form of skin cancer, although it can often be cured if caught very early. To understand how melanomas form, it is useful to know something about the skin.
The Skin. The skin is the largest organ in the body and consists of layers.
- The outermost layer of the skin, the epidermis, is only about 20 cells deep, roughly as thick as a sheet of paper.
- The dermis ranges in thickness from one to four millimeters (about 1/32 to 1/8 inch). The dermis contains tiny blood and lymph vessels, which increase in number deeper in the skin.
Melanocytes. A layer of cells between the epidermis and the dermis called melanocytes produce a brown-black skin pigment called melanin that determines skin and hair coloring. Melanin also helps protect against the damaging rays of the sun.
Melanoma. Melanocytes give melanoma its name. As a person ages, melanocytes often proliferate, forming concentrated clusters that appear on the surface as small, dark, flat, or dome-shaped spots, which are usually harmless moles or liver spots.
- When cell proliferation occurs in a controlled and contained manner, the resulting lesion is benign and is commonly referred to as a mole or nevus. Most adults have at least several dozen benign moles.
- Sometimes, however, pigment cells grow out of control and become a malignant and life-threatening melanoma.
 | Click the icon to see an image of melanin. |
At first, melanoma cells grow sideways (laterally), and so are confined to the epidermis and to the top layers of the dermis. However, once they grow downward into the dermis, the cancer will come into contact with lymph and blood vessels. The thicker the melanoma, the greater the likelihood that it could spread through these vessels to distant sites. Removal of the lesion before it penetrates to the deeper layers of the skin is crucial for achieving a cure. Early detection is very important.
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