Congenital Melanocytic Naevus

Introduction

Congenital melanocytic naevus (kuhn-jeh-nuh-tl meh-lan-oh-sit-ik nee-vus) is also known as a brown birthmark or mole. Congenital melanocytic naevus (which is abbreviated to CMN) may be present at birth or appear a few months after birth. The name Congenital Melanocytic Naevus gives us a lot of information about what it is:

Congenital means it is present from birth.
Melanocytic is the adjective of the word melanocyte.
A melanocyte is a cell that produces brown pigment and makes up your skin colour.
Melanocytes are found in the skin and otherparts of the body.
Naevus is the medical word for mole - it is made up of a cluster of melanocytes.

Infant with brown birthmark of congenital melanocytic naevus covering majority of back and arms

Who gets it?

Boys and girls from all ethnicities have an equal risk of getting a CMN.
1 in 100 babies get a CMN.
Larger CMN are rare - a CMN that has an adult size bigger than 20cm happens in about 1 in 20,000 babies.

What causes it?

A CMN is basically a “manufacturing error” or a genetic defect that happens before birth when your baby is developing in the womb. This error causes the overgrowth of the melanocyte cells in a particular area of skin. Sometimes this error can cause the overgrowth of cells that make hairs. Most babies with a CMN have no overall genetic problem outside this error and are healthy and well.

What does it look and feel like?

Looks like…

At birth your child's mole can have different shades of brown and black and it may darken or lighten over time. Very rarely, in babies with lighter skin, a CMN can be pink or red.
Most CMNs occur on the body, arms and legs of babies rather than their head and neck.
There may be more hair inside the mole than normal skin.
Larger CMNs may have small moles scattered around them. These are called “satellites” or dissemintated lesions and it is normal for you to see more appearing after birth in the first few years of your child's life.
CMNs will grow in proportion to your child as your child gets older.
Although most children will have them throughout life, in rare cases your child's mole may disappear altogether.

Feels like…

Often a CMN starts flat but later can become raised and bumpy.
Larger CMNs can develop lumps of skin within it.
Most CMNs do not cause symptoms but sometimes they can be itchy, especially the bigger ones.
The skin over a CMN can feel dry and be fragile which means it may bleed.

What are the risks of a CMN?

Poor self-image : Your child may experience distress because of the cosmetic appearance of the CMN, particularly if their CMN is large and visible.
Risk of malignancy: Like any mole there is a risk that your child may develop a melanoma. But this is very uncommon with most CMNs.
For small and medium sized CMN, the lifetime risk of getting a melanoma is less than 1 in 100.
For larger CMN, the lifetime risk of getting a melanoma is slightly higher at 2 to 5 in 100.
Risk of involvement of the brain and spinal cord: When there is an overgrowth of melanocytes in the brain, spinal cord, and skin it is called Neurocutaneous Melanosis. This is very rare, but is more likely in children with a giant CMN, satellite moles, or more than one medium sized CMN. Having symptoms from Neurocutaneous Melanosis is rare but it can include fits, headaches, vomiting, and developmental delay.

What tests might be needed?

A doctor will usually diagnose your child's CMN from history and clinical examination alone. Sometimes a paediatric dermatolgist may use a dermatoscope (a handheld device which magnifies an area of skin) to confirm the diagnosis. Occasionally, they may need to biopsy the mole. An MRI scan of the brain and spinal cord may be done if there are any worrying features for brain or spinal cord involvement.

What treatments are available?

What can I do?

Regularly see a paediatric dermatolgoist for monitoring of your child's mole.
Perform regular skin checks yourself looking for any change in appearance, such as:

-Growing in size

-Changing colour

-Change in the edges of the mole

-Change in the surface of the mole such as new bumps or crust

-Sores, bleeding, oozing, or scabbing

Tell your specialist if you notice any changes in your child's mole.
Be sun-safe! Always remember to Slip, Slop, Slap, Seek, Slide! (see Sun Safety factsheet)

-Slip on sun protective clothing that covers as much of your child’s body as possible

-Slop on SPF 30 or higher sunscreen 20 minutes before going into the sun and reapply it

every two hours

-Slap on a broad brimmed hat that protects your child’s face, neck, and ears from the

sunlight

-Seek shade - this is really important when it’s really sunny (between 11am and 3pm)

-Slide on some sunglasses

Medical therapies

Large CMN need regular follow up with a dermatologist, paediatrician, and general practitioner as they have a higher risk of getting complications. Treatment is not always needed but is sometimes preferred if your baby has a large CMN. Treatment options are dependent on many factors such as the size of the CMN, how deep it goes, where it is located, and the age of your child.

Surgical removal of the mole: complete removal is difficult for large CMNs and sometimes impossible. It is best undertaken with a paediatric plastic surgeon.
Non-surgical treatments:

-Dermabrasion (“sanding” of the mole)

-Chemical peels

-Laser therapy

What happens after treatment?

Surgical removal may either be a complete or partial removal of the mole.
Non-surgical treatments do not remove the mole but try to improve the appearance of the mole by lightening the colour.
The mole may become lighter with time without any medical treatment; however, most persist for life.
Regular skin checks are still required after any treatment including complete surgical removal.
Always remember to be sun smart!

What support is available?

Your GP and dermatologist will work together to look after your child with CMN. Nevus Support Australia is a patient support group that helps people and families affected by CMN. Nevus Support Australia:

Postal address: PO Box 262 Seacliff Park, South Australia 5049 Phone: (08) 8298 3080 Website: http://www.nevussupport.com Email: michelle@nevussupport.com

Authors/Reviewers:

Author: Dr Sarah Hanna
Paediatric Reviewer: Dr Mayuri Sivagnanam
Editor in Chief: Dr Tevi Wain