Nevus

A nevus is more commonly called a mole

dermatologist examining mole
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A nevus is a benign (non-cancerous) melanocytic tumor, more commonly called a mole. Nevi (the plural of nevus) are not usually present at birth but begin to appear in children and teenagers. Most moles will never cause any problems, but a person who has 50 or more moles is more likely to develop melanoma, the most aggressive form of skin cancer.

What is Skin Cancer?

Skin cancer — the abnormal growth of skin cells — most often develops on skin exposed to the sun.

But this common form of cancer can also occur on areas of your skin not ordinarily exposed to sunlight. There are three major types of skin cancer — basal cell carcinoma, squamous cell carcinoma and melanoma. Early detection of skin cancer gives you the greatest chance for successful skin cancer treatment.

Causes of Skin Cancer

Melanoma occurs when something goes awry in the melanin-producing cells (melanocytes) that give color to your skin.

Normally, skin cells develop in a controlled and orderly way — healthy new cells push older cells toward your skin's surface, where they die and eventually fall off. But when some cells develop DNA damage, new cells may begin to grow out of control and can eventually form a mass of cancerous cells.

Just what damages DNA in skin cells and how this leads to melanoma isn't clear. It's likely that a combination of factors, including environmental and genetic factors, causes melanoma.

Still, doctors believe exposure to ultraviolet (UV) radiation from the sun and from tanning lamps and beds is the leading cause of melanoma.

UV light doesn't cause all melanomas, especially those that occur in places on your body that don't receive exposure to sunlight. This indicates that other factors may contribute to your risk of melanoma.

Skin Cancer Screening

You and your doctor may consider screening options such as:

  • Skin exams by a trained professional. During a skin exam, your doctor conducts a head-to-toe inspection of your skin.
  • Skin exams you do at home. A self-exam may help you learn the moles, freckles and other skin marks that are normal for you so that you can notice any changes. It's best to do this standing in front of a full-length mirror while using a hand-held mirror to inspect hard-to-see areas. Be sure to check the fronts, backs and sides of your arms and legs. In addition, check your groin, scalp, fingernails, soles of your feet and spaces between your toes.

Some medical organizations recommend periodic skin exams by your doctor and on your own. Others don't recommend skin cancer screening exams because it's not clear whether screening saves lives. Instead, finding an unusual mole could lead to a biopsy, which, if the mole is found to not be cancerous, could lead to unnecessary pain, anxiety, and cost. Talk to your doctor about what screening is right for you based on your risk of skin cancer.

Types of Nevi

There are multiple types of nevi. A dysplastic (or "atypical") nevus is a large, irregularly-shaped type that particularly increases a person's risk of melanoma: About 50 percent of melanoma cases occur in people who have dysplastic nevi. People with this condition should have a thorough skin exam by a dermatologist every six months.

Moles usually appear late in childhood, but some are present at birth in those with a condition called "congenital melanocytic nevi." The lifetime risk of getting melanoma for people with congenital melanocytic nevi has been estimated to be up to 10 percent, depending on the size of the nevus.

Reference:

Mayo Clinic. Skin Cancer. http://www.mayoclinic.org/diseases-conditions/skin-cancer/basics/definition/con-20031606

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