Congenital Melanocytic Nevus

What is a congenital melanocytic nevus (birthmark mole)?

A congenital melanocytic nevus (birthmark mole) is a brown, flat or bumpy spot, sometimes with increased hair growth, on any part of the body. It is a cluster of numerous melanocytes (cells that produce the color of the skin). It may be present at birth, or it becomes apparent shortly after the birth. Up to 3 out of 100 newborns will have it. The child can have one or more such spots. The size varies from very small to giant. When it is giant in size, it can involve large parts of the body. Technically, giant moles are considered those larger than 20 centimeters (about 8 inches).

What is the cause of my baby’s congenital melanocytic nevus (birthmark mole)?

The cause is unknown.

Should I take my baby to a health care provider?

It is always wise to see your baby’s health care provider for an initial exam and for a correct diagnosis. Sometimes congenital melanocytic nevus can turn into malignant melanoma, which is sometimes deadly skin tumor. The chance of developing melanoma increases with increase in the size of congenital melanocytic nevus. The risk is the highest in those whose mole will be over 40 centimeters (about 16 inches) in diameter by the adulthood. You should report to your health care provider any change in the appearance, as well as any development of deeper bumps under the congenital melanocytic nevus. Any baby with a giant mole or those with numerous moles, especially over the spine should be checked for neurocutaneous melanosis, which is increased growth and clustering of melanocytes (cells that produce the color of the skin) both in the skin and central nervous system (brain and its envelope). In the majority of cases, neurocutaneous melanosis may not produce any problems, but sometimes it can cause a blockage of cerebrospinal fluid circulation in the brain, causing brain cysts, increased size of the head (hydrocephalus), seizures and paralysis.

Is congenital melanocytic nevus (birthmark mole) painful to my child?

Congenital melanocytic nevus is not painful.

My baby has congenital melanocytic nevus (birthmark mole), so what is the treatment?

In the majority of cases no treatment is needed, except for watching for any change in the appearance and symptoms. It is important to mention that the mole sometimes may continue to look the same; however, the change can happen under the skin. Therefore, you also have to feel it/touch it to notice any bump under the skin. You should report any change in the mole to your health care provider. Larger moles that have a higher chance of turning into the cancer, and those that are cosmetically bothersome should be considered for surgical excision even without any changes in the appearance or symptoms.

For more specific questions on congenital melanocytic nevus (birthmark mole), or other birthmarks, please send us your question using our blog below.

  • Hi, I have a congenital melanocytic nevus that I was born with on my lower back on one side of my trunk, its a perfect oval shape an even colour brown with hair and brown spots inside it and is just about 10cm. I’ve had it looked at by two dermatologists one is very well known and meant to be very good. He has checked it the past two years and said it looks perfectly fine to him. One of my close friends developed melanoma recently she always used sunbeds and has ginger hair. Since then I have had extreme anxeity about my birthmark because anything I see online says it has an increased rate of becoming a melanoma with a bad prognosis and I think sometimes the anxeity gives my phantom pain coming from the area since when I touch it its not tender and no changes. My question is would removing it reduce the risk of it changing? How much of a risk is it? I was told you are at an increase risk of it changing during or after a pregnancy and I had my son 4 years ago.

    • Dr. T

      Congenital melanocytic nevi can indeed change into melanoma, but the risk of that change depends on the mole (nevus) size. If any of moles (nevi) cause anxiety in my patients, then I excise them. If completely excised then the chance of melanoma arising at the site is equal to zero.
      I wish you all the best!

      Dr. T

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