Melanoma is cancer that arises from the pigment-producing cells in the uppermost layer of the skin. These cells are called melanocytes.

Melanoma that originates in the skin is called cutaneous melanoma. It also may occur in the eye, a condition called ocular melanoma or intraocular melanoma. In rare cases, melanoma may begin in the digestive tract called meninges, lymph nodes or other parts of the body where there are melanocytes.

Ultraviolet radiation, which is present in sunlight and in tanning beds, probably sets off many cases of melanoma by causing genetic damage in melanocytes. Children and adolescents are especially sensitive to the effects of ultraviolet light.

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Melanoma is a potentially life-threatening cancer because it can travel from the skin to other parts of the body. With early diagnosis, however, survival rates are encouraging. The goal is to recgonize melanoma early. Often, the first signs of melanoma are changes in a mole or the appearance of a new colored spot on the skin.

When melanoma spreads, cancer cells are found in the lymphatic system. If the disease spreads to other parts of the body, it's called metastatic melanoma.

The chance of developing melanoma increases with age, but it affects people of all ages and is one of the most common cancers in young adults.

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Often, the first sign of melanoma is a change in the size, shape, color or feel of an existing mole. Most melanomas have a black or blue-black area. Melanoma also may appear as a new, black, abnormal or "ugly-looking" mole.

Rarely, melanoma is not pigmented and is more difficult to diagnose. It may appear as a non-healing ulcer or a new scar-like lump in the skin.

The warning signs are sometimes referred to as ABCDE:

  • Asymmetry — Two halves of a lesion that are not the same
  • Border — Borders of a lesion are irregular, scalloped or vague
  • Color — Color varies from one area to another, including shades of tan or brown as well as black, blue, red and white
  • Diameter — A lesion that is greater than 6 millimeters in diameter, about the size of a pencil eraser
  • Evolution — Lesions that change or evolve

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If your doctor suspects that a spot on the skin is melanoma, you will need a biopsy, which is the only way to make a definite diagnosis. In this procedure, your doctor tries to remove all of the suspicious-looking growth. If the growth is too large to be removed entirely, your doctor may remove a sample of the tissue.

A biopsy usually can be done in the doctor's office using a local anesthetic. A pathologist then examines the tissue under a microscope to check for cancer cells.

Often, the pathologist can easily tell whether these cells represent melanoma or a non-cancerous mole. Sometimes, however, the distinction can be tricky, and special stains or further diagnostic tests must be performed to make the diagnosis. Distinguishing between cancerous and non-cancerous tumors can make all the difference for a patient, as the treatment and outcomes can be very different.

A pathologist can identify many other characteristics of the melanoma to determine how likely the cancer can be successfully treated. If you've had a biopsy at another medical center, we will ask an experienced pathologist at UCSF to review them as well.

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Surgery to remove melanoma is the standard initial treatment. It is necessary to remove not only the tumor but also some normal tissue around it, called the margin, to reduce the chance that any cancer remains. The width and depth of surrounding skin to be removed depends on the thickness of the melanoma and how deeply it has invaded the skin.

When the melanoma is very thin, the biopsy may remove all the cancerous tissue and no additional surgery may be necessary. For thick melanomas, it may be necessary to take out a larger margin of tissue. Deeper melanomas have a higher chance of spreading to the lymph nodes. For these cases, a sentinel lymph node biopsy may be performed to determine if the cancer has spread.

Surgery alone may not effectively control melanoma that has spread to other parts of the body. Your doctor may use other methods of treatment, such as chemotherapy, biological therapy or immunotherapy, radiation therapy or a combination of these methods.

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Reviewed by health care specialists at UCSF Medical Center.