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Understanding Melanocytes

Melanoma begins when melanocytes (pigment cells) gradually become more abnormal and divide without control or order. These cells can invade and destroy the normal cells around them. The abnormal cells form a growth of malignant tissue (a cancerous tumor) on the surface of the skin. Melanoma can begin either in an existing mole or as a new growth on the skin.
In men, melanoma is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the arms and legs. Melanoma usually occurs in adults, but is sometimes found in children and adolescents.


A doctor should be consulted if any of the following possible melanoma symptoms occur. Symptoms of melanoma include a mole that:
  • Changes in size, shape, or color
  • Has irregular edges or borders
  • Is more than one color
  • Is asymmetrical (if the mole is divided in half, the two halves are different in size or shape
  • Itches
  • Changes in pigmented (colored) skin
  • Develops satellite moles (new moles that grow near an existing mole)
  • Oozes, bleeds, or is ulcerated (a hole forms in the skin when the top layer of cells breaks down and the underlying tissue shows through).

Diagnosing Melanoma

A doctor or nurse specialist can tell whether an abnormal-looking mole should be closely watched or should be removed and checked for melanoma cells. The purpose of routine skin exams is to identify and follow abnormal moles. The removal of the entire mole or a sample of tissue for examination under a microscope is called a biopsy. If possible, it is best to remove moles by an excisional biopsy, rather than a shave biopsy.
(Click Melanoma Diagnosis for more information on this topic.)
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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