All About Congenital Melanocytic Nevi

What is a Congenital Melanocytic Nevus (CMN)?

Nevus (also spelled naevus; plural, nevi or naevi) in the broad sense, means “birthmark”, and can be used to describe virtually any mole or birthmark.

  • If it is present at birth, it is called congenital. One in every 50 to 100 people is born with a small CMN.
  • If a birthmark is caused by a pigment-producing cell, it is called a pigmented or melanocytic nevus.
  • Congenital Melanocytic Nevi can range in size from the small, common ones the size of a pinhead, up to large, rare forms that cover much of the body surface. The largest ones are described medically as giant nevi, and happen approximately once in every 20,000 births; the larger they are, the rarer.

What does a Congenital Melanocytic Nevus look like?

Every congenital melanocytic nevus is unique. People of all races and colors of skin can be born with one. CMN generally grow in proportion to the child. In other words, they will usually continue to cover the same proportional part of the body surface as at birth—for instance, a part of a limb, or extending between the shoulder blades and the upper thigh.

Rare exceptions to this are “tardive” congenital melanocytic nevus, as these become visible after birth and can therefore appear to grow. Occasionally, where part of a CMN is very pale, it can darken during the first few months and thus appear to grow. The size that a CMN will end up can therefore be estimated from the size at birth by looking at its size and where it is located.


Congenital melanocytic nevi can be on any part of the skin, including palms, soles and scalp, and even inside the mouth.


Usually some sort of shade of brown to black, sometimes congenital melanocytic nevi can be reddish. It is often very mixed inside the nevus, with smaller patches of different colors on a solid background. CMN at birth are often deep black, or even dark purple/red as they have many blood vessels visible through a thin surface. They can change color over time, as the child grows. When they change, they usually become paler, but can also become darker for those that were initially light or speckled. Lightening appears to happen more in children with light or red hair and pale skin than in those with darker hair and skin tone.


Congenital melanocytic nevi usually have hair growing out of them, although this is often not visible at birth and can remain unnoticeable throughout life. The hair color can be darker than the child’s head hair, or the same, or very occasionally lighter. If a CMN is on the scalp, there is usually more luxuriant hair growth over the lesion and the hair grows faster than on the rest of the scalp. Body CMN—be they small or large—can develop terminal hair, which is more visible and often dense. Occasionally, congenital melanocytic nevus are completely hairless, even ones that occur in the scalp, or can have patchy hair loss or hairs without pigment (grey or white hair).


The texture of large congenital melanocytic nevi tends to be different from that of normal skin, sometimes being softer, looser and more wrinkled. The CMN can be nearly flat or can be very folded or lumpy.


The total number of visible nevi can continue to increase after birth, although this does not always happen. When it does, they often develop most during the first few years of life, when the rate of appearance of different ones then usually tapers off. However, they are always relatively small. Such “new” nevi, sometimes called “satellites”, are considered by doctors to also be tardive. That is, they may have already been there as scattered, unpigmented congenital melanocytic nevi at the time of birth. Appearance of these additional nevi is more likely to occur in children with very large and multiple CMN, but in themselves are not a reason for concern.

What Causes Congenital Melanocytic Nevi?

Research into the molecular and embryological causes of congenital melanocytic nevus has made great strides in the past few years! Check back here for more details summarizing these findings. For highly in-depth proceedings, you can apply to your patient association representative for access to the 2013 CMN Expert Meeting slidecasts or copies of other publications of interest to you, or read a selection of relevant primary publications uploaded to the RE(ACT) Community for rare and orphan diseases.

Medical Challenges

Cutaneous Problems


Many congenital melanocytic nevi are more delicate than normal skin, especially in newborns. They can therefore tear more easily if they are knocked or scraped. However, they do not bleed any more than normal skin, and they tend to heal well with minimal scarring. Treat as any superficial scrape or wound on non-nevus skin, cleaning with soap and water, and use of an antiseptic ointment and a bandage.


Some congenital melanocytic nevi are drier than the surrounding skin, need to be washed without soap, and moisturized regularly (your doctor can advise you on this). Occasionally, CMN are very itchy. This can be due to dryness, too rich a cream to treat the dryness, eczema in the nevus, or sometimes for no apparent reason (though this is a subject of current research). Such itchiness can usually be relieved using prescription creams and ointments, cold pack treatment, baths in corn starch or colloidal oatmeal, or vibrations.

Decrease in subcutaneous fat:

This is usually only seen with larger congenital melanocytic nevi. For some reason, the presence of the CMN interferes with setting up the layer of fat that is normally present between the skin and underlying muscle and bone. This can result in the nevus appearing to be depressed below the general skin surface, the limb, buttock or side of the face, and appearing obviously thinner than normal. The thinner area functions just as normal—for example, a thinner leg will be perfectly strong, as the thinness is only due to less fat and not less muscle.

Absence of sweat glands:

Although not systematic, the largest or bumpy forms of congenital melanocytic nevi can sometimes have fewer sweat glands within the nevus. Thus, the CMN owner can have problems with overheating on warm days or during sports activities.

One solution is to bring moisture to the outside of the skin—a wet hat or T-shirt, or water in a spray bottle, can help replace the difficulty in sweating by allowing evaporation from the surface affected. Other areas of the body may sweat more in compensation, so internal hydration through drinking more water is also important.

Neurological Problems

Problems in the brain or spinal cord are the most common serious complication seen in children with congenital melanocytic nevus. Because the pigment cells found in the skin and (yes, normally in) the meninges develop from the same cells as the brain in the early embryo, people with CMN can also have differences in their brain or spinal cord. Approximately one in fifteen to twenty people with large and giant forms of CMN have excess pigment cells in the brain or spinal cord. This can lead to a complication known as neurocutaneous melanocytosis (NCM). Earlier studies often used the term “melanosis”—the first means more pigment cells, and the second means more pigment. The difference is not easy to determine non-invasively.

Other much rarer problems include benign brain or spinal tumors or cysts, too much fluid in the brain (hydrocephalus), or abnormal brain structure. All of these neurological problems are more common with larger and more numerous CMN, but there is no connection with the site of the CMN. In other words, having a congenital melanocytic nevus overlying the brain or spine does not increase the chance of having neurological problems.

Should a Person with a CMN have Magnetic Resonance Imaging (MRI)?

Current recommendations in the U.K. and some, but not all, other countries, are that any child born with two or more congenital melanocytic nevus in any location should have a routine MRI scan of the brain and spine, preferably by the age of six months, though there is no strict cut-off age. It is not possible to say that MRI abnormalities could never occur in children with only one CMN at birth, but the likelihood is much less. Minimal recommendations for MRI settings can be downloaded as a printable sheet here, and can be brought with you to give the neuroradiologist.

The overall chance of finding any kind of abnormality on brain and spinal MRI scan in children with large and multiple CMN may be as high as 25%, but only around half of these will have any actual neurological problems.Things to look out for include: epileptic convulsions (fits/seizures), developmental delay, limb coordination issues, frequent vomiting or headaches not linked to an infection or fever, and tiptoeing or late bed-wetting, which can be signs of a tethered spinal cord. (And which are also quite frequent in children and should not alarm you.)

It is possible to have problems in development even when the scan is normal, but these tend to be milder. The reason for doing the scan is to pick up the rare cases of tumors, cysts and extra fluid on the brain that require an operation, and to allow more careful neurological monitoring of those children with MRI findings. The pigment cells in the brain or spine cannot currently be treated themselves, but the epilepsy that sometimes occurs in NCM can respond to conventional medication and surgical approaches, as can a tethered spinal cord or cysts.

We also recommend that children with congenital melanocytic nevi larger than 20 cm (8 inches) projected adult diameter be followed up regularly to watch their neurological development, even if they do not have more than one nevus. In addition, any child with any type of CMN who has neurological symptoms like those described above should have an MRI.

These neurological problems tend not to afflict adults with CMN if they had not started during childhood or adolescence.

Malignant Melanoma

Melanoma is a cancer of melanocytes, the skin cells which produce pigment and which make up congenital melanocytic nevus. It used to be thought that melanoma was very common in people with CMN, but we now know that it is rare, occurring in around 1-2% of all people with CMN over their lifetime. However, the risk is higher in people with very large and numerous CMN, perhaps as much as 10%, and there is a peak of risk during childhood. When considering these risks, you need to bear in mind that a person without a CMN still has a risk of about 40% of developing some kind of malignant cancer at some time in his or her lifetime.

Melanoma in people with congenital melanocytic nevus can occur anywhere, not just within the CMN, and not just in children. It can present as a lump in the CMN, in another area of skin, or in the lymph nodes (which are throughout the body). However, melanoma is rarely if ever found in a disseminated “satellite” nevus. In about half the cases, it occurs directly within the brain or spine, when it can present with persistent headaches with nausea/vomiting, or visual disturbances, balance problems or seizures, like other tumors.

Unfortunately, when malignant melanoma occurs in a person with a congenital melanocytic nevus, it is often aggressive and difficult to treat. Our recommendations are that any rapidly changing area should be reviewed by an experienced doctor, who can decide whether a biopsy is required. Do remember however, that nodules, lumps and color changes appear frequently in congenital melanocytic nevi, and they are almost as frequently, completely harmless. Serial photographs, the use of dermoscopy, palpation of nevus and scars, examination of lymph nodes and a thorough review of systems may aid physicians in early detection of melanoma. Also, only experienced pathologists can avoid the trap of finding a growing CMN nodule “melanoma-like”; if such a report comes to you, it is worth asking for a second opinion.

We recommend that children who develop any new neurological problems such as recurrent headaches, visual disturbances, seizures, or developmental changes should be seen urgently by specialist doctors, such as a pediatric neurologist and a neuroradiologist, in a multidisciplinary institution if at all possible.

Psychological Challenges

People with congenital melanocytic nevi sometimes attract looks, stares, whispering and finger-pointing.

Children who grow up with a prominent congenital melanocytic nevi or many congenital melanocytic nevi may well have problems adjusting to the disfigurement that they perceive, particularly during the teenage years. This, however, is a very individual thing, and varies depending on the child’s personality and on the support from family and friends. The problems may manifest as anxiety, depression, or lowered self-esteem.

Family members sometimes hope that a nevus will ‘fade’ and the other potential medical challenges will also disappear. Some large congenital melanocytic nevi can lighten over time, but the birthmark itself, and potential challenges, remain. This reality requires not only the person with the CMN, but also their loved ones, to take some time to adapt.

It would be ideal if we were able to offer all people at risk some degree of automatic counseling during their childhood, and accompaniment to support their families as well. Some major hospitals (Great Ormond Street, London U.K.; Hôpital Necker – Enfants Malades, Paris, France; University Children’s Hospital, Zürich, Switzerland) currently have a psychology service available for their Congenital Melanocytic Nevus patients. However, not all families want psychological input, and many hospitals and most private settings do not have this facility.

Changing Faces is an example of a support group specializing in all types of disfigurement which has some excellent guidelines and information in English. Its website is Some documents have been adapted for people affected by CMN; these are available here and in French with some revisions, here.

Treatment Options

One of the most frequently asked questions is “What can be done about it?” We all want to think modern medicine has miracles to offer us, but there are no magic answers, yet.

Many people with large nevi have problems with itching or other discomfort. Lotions and creams can alleviate some of that discomfort. But it is important to note that there are currently no creams, lotions or other topical products one can rub on the skin that can remove a nevus. (There are quite a lot of things one could rub on the skin that would irritate or damage it, so any kind of “whitening agent” is highly discouraged, as they are always aggressive and sometimes toxic.)

However, patients around the world have joined together in this federation to help advance a number of research initiatives. We want more options and better treatments!

Monitoring a CMN without surgical intervention

Removing a congenital melanocytic nevus is a personal decision to be taken ideally after consultation with more than one informed, trusted physician. Many patients who have a large CMN, or their families if they are too young to decide for themselves, prefer to leave it unoperated for various valid reasons.

CMN removal

When small nevi are removed, the edges of the surrounding skin are simply pulled together and stitched. Removal of a large nevus involves the replacement of the affected skin. Skin can be transferred from another area of the body (grafting), or adjacent skin can be stretched, then used to cover the area where the nevus was removed (tissue expansion). There are many details about the surgery you should consider and it is best to consult a surgeon experienced in the treatment of giant nevi. The subject and all possible techniques have not been covered in depth in this summary.

We recommend seeking multiple professional opinions and asking about pain management, before beginning any intervention for removal.

Lasers are successful for many superficial skin imperfections, but cannot completely remove a congenital melanocytic nevus. Lasers can destroy the surface cells of some nevi and such treatments are sometimes suggested by physicians. Some people report successful results in depigmentation with laser treatment, but others report poor results. When a CMN is not removed through the depth of the skin, no matter the technique used, the remaining cells have a tendency to repigment the region partially or fully. Laser treatments in children require general anesthesia.

Laser treatment of unwanted hair presents similar questions of exposing the surrounding tissues to suboptimal doses of the light or heat generated by the laser, but some patients do choose this approach. Repeated treatments are generally necessary. Electrolysis is slow and painful, and is therefore not suitable for large areas. The least aggressive manner to remove terminal hair from CMN is by trimming short with a gentle electric razor, and hydrating the skin. Chemical hair removal creams should not be used as they can irritate the skin. Shaving does not affect the amount, rate or thickness of hairs that grow back.

It is important to remember that a congenital melanocytic nevus cannot be removed without leaving a scar. Scarring may be minimized at the hands of a highly skilled, experienced surgeon, and may also be remodeled at other points during a lifetime, so it is recommended you seek out a surgeon you will trust over a long period.

Management of Neurological Symptoms

A personalized plan should be developed with the neurologist to help in adapting to any constraints imposed by such symptoms.

Living with a Nevus

Sun Protection

People with congenital melanocytic nevi can and should enjoy a normal life. Affected children particularly, but all people with CMN, should use good sun protection—the same as we would recommend for all children. In particular, it is important to avoid sunburn. As a general rule: sun avoidance, coupled with good clothing protection, is more effective than sunscreen. The best sunscreens contain a reflectant barrier such as titanium dioxide; select a high protection factor (SPF), ideally 25 or more, and with high UVA protection if indicated. Sunscreen needs to be refreshed every 2 hours or so, more often when swimming or sweating.

Sun Avoidance

People with congenital melanocytic nevi should stay out of the direct sun as much as possible during the hottest hours of the day and in the hottest months of the year.

The hottest hours of the day are 10am-4pm. In most of the Northern Hemisphere, the hottest months of the year are April to October. For the Southern Hemisphere, October to April are the months in which to take care to reduce sun exposure.

  • UV exposure is much higher beside water or snow, so special care should be taken when swimming outside or skiing.
  • The sun is more harmful at higher altitudes.
  • The sun remains almost as harmful when it is cloudy, so even if the day is cloudy, the CMN patient should wear appropriate clothing such as a sunhat during the hottest times of the year.
  • Shade provides less protection when near water or snow, or when the weather is cloudy, because the sunrays are reflected into the shade.
  • The increased risk of skin cancer in people with CMN probably applies to their whole body, not just to their CMN.

How to Help a Person with a CMN

The short answer is, find out more.

If you are a new parent of a child with a nevus, you are taking in a lot of information at once. Some of it follows, and not everything relevant for you is even all there. It is important to stop and get yourself oriented. Focus on adjusting to your baby and making him or her welcome in your family, then begin to sort out the most pressing questions you have, and start there.

You may yourself have a congenital melanocytic nevus, but had not known its name, or that there were other people like you. There are, all over the world, and you can meet and learn from them.

We suggest you get connected to the many thousands of other people who know what you are going through via your national support groups. If your country doesn’t have one, all of the existing patient associations welcome inquiries from other countries. There is a massive amount of reassurance available to anyone who simply gets connected. For a list of online communities and patient association webpages, please click here.

Don’t go it alone! We are here for you, and have been through what you are experiencing.

A wealth of additional information can be found all through our Naevus Global federation website and on the individual member association websites.


The information presented here was developed with the assistance of Veronica Kinsler, M.D., Ph.D.; Heather Etchevers, Ph.D.; Harper Price, M.D.; Caring Matters Now; Children of Light; Nevus Outreach, Inc. It is not meant to replace any personal medical advice which you get directly from your doctor(s) for yourself or your child.