What is CMN?

A congenital melanocytic naevus (usually abbreviated to CMN: plural CMNs) is one of a wide variety of different types of birthmark that may occur in newborn babies:

• congenital indicates that the abnormality is present at birth.
• a melanocyte is a type of cell which is present in normal skin and in certain other organs - its function is to produce melanin – the brown pigment responsible for skin colour in all races.
• melanocytic is the adjective derived from the word melanocyte.
• a melanocyte precursor is a less fully committed type of cell that can develop into a melanocyte or into one of a number of alternative cell types.
• naevus is a (Greek) word used to describe any type of birthmark that occurs in the skin; the plural is naevi

A CMN is composed of an abnormally large collection of melanocytes and melanocyte precursors within the skin, and can be regarded as a type of benign tumour.

In the embryo, melanocyte precursors originate in the region of the developing spine, from where they migrate to the skin. Their route is along the nerves that emerge from the spinal cord and connect it to the skin. As they arrive in the skin, the melanocyte precursors normally spread out and become evenly distributed among the other skin cells. Their numbers are small. Their function is to produce melanin pigment, which protects the skin from damage by ultraviolet rays. The amount of pigment they produce depends on the degree of natural skin colour, and the degree of recent exposure to sunlight (ie. degree of tanning).

It seems likely that a CMN reflects a failure of the normal processes of proliferation and maturation of melanocyte precursors as they reach the skin. Instead of flowing out smoothly and evenly into the skin, too many immature cells develop and persist in a large group. This might happen because they receive an abnormal signal to proliferate at this point in their journey, because their maturation into fully finished melanocytes is impaired, because the final leg of their migration is impeded, or perhaps because of a combination of these.

Birthmarks can be regarded as manufacturing errors, the visible effect of aberrations that have occurred during a child’s development before birth. This type of aberration almost certainly occurs because of a mutation that has occurred in a gene during the early growth of the embryo.

Each of our thousands of genes contains the information required to make one particular protein. Each protein has its own distinct function, and certain proteins will have responsibility for controlling the way that particular body tissues are organised during their development in the embryo. This organisation process is to a great extent achieved by the activation - in a specific sequence - of the various genes involved.

A mutation is a change in a gene that leads to a small but potentially serious error in the construction of the protein that is its product. Faulty proteins will be unable to perform their function correctly.

If a mutated gene is present in the egg or sperm from which an embryo develops, every cell in the developing embryo will be affected; this may lead to miscarriage. If the baby survives to birth, it will be affected by a specific genetic disease, depending on exactly what function the gene’s protein product would normally perform. On the other hand, a mutation that occurs after conception in the developing embryo will lead to just a part of the baby being affected. This type of mutation is called a somatic mutation. Birthmarks are probably mostly due to somatic mutations, though it is now known that other complex abnormalities in gene function can also be responsible.

Mutations occur by chance, in a random and unpredictable way, and can be regarded as normal events. However, the risk of mutations occurring is increased under certain circumstances, for example by exposure to radiation, to certain drugs and, perhaps, to chemicals that may be present in food.

CMNs are classified according to size. Strictly speaking a ‘small’ CMN is one that measures less than 2.5cm (1 inch) across; a ‘medium’-sized CMN measures between 2.5-20cm across, and a ‘large’ (sometimes called ‘giant’) CMN will measure more than 20 cm across. Using these definitions, a small CMN will be found in about 1 in 100 newborn babies, which makes it one of the commonest types of birthmark. Medium CMNs occur in approximately 1 in 1,000 newborns, whereas large CMNs only occur in 1 in about 20,000 newborns.

A major problem with this kind of classification is that the skin surface area increases greatly during growth. The length of a newborn baby is about 50cm, whereas the average length of an adult is about 175cm. Therefore a 20cm CMN (classified as ‘large’) in an adult will have only measured 5.5cm at birth (classified as ’medium’). This is about the same length as the hand, ie. the distance from the finger tips to the wrist. None of this really matters much except that it does mean that what are called ‘large’ CMNs in adults are not the same thing at all as ‘large’ CMNs in the newborn.

A CMN is primarily an abnormally large accumulation of melanocytes and melanocyte precursor cells in the skin. CMNs show a number of characteristics which vary considerably, and which may change somewhat in any CMN over a period of time. These include:

• size
  CMNs vary greatly in size, from a few millimetres to many centimetres across. The very largest may cover most of a limb or much of the trunk. However, as the figures above indicate, smaller ones are far commoner. As the child grows, a CMN will enlarge in proportion to the child’s general growth. Occasionally, during the first year or two, there may be some true extension of the pigmentation at the outside edge, but this does not usually lead to a substantial increase in the overall size of the CMN.
• site
  Most of the children I see have lesions on the back, or on the head and neck. The lesions on the back are almost always centred in the midline, and if very extensive, they tend to wrap around the sides of the body and may meet again in the front. Very large CMNs cover parts of the body in such a way as to resemble items of clothing, most frequently boxer shorts or old-fashioned bathing trunks; these are often therefore termed ‘garment naevi’, or ‘bathing trunk naevi’. However, in practice CMNs can occur at any site on the skin.
• pigmentation
  

  The colour of a CMN depends to a great extent on the background skin colour of the child. CMNs therefore tend to be lighter brown in blond-haired children, darker in Asians and in Orientals, and almost black in Afro-Caribbeans

  Immediately after birth, they often have a rather purplish hue. They are almost always much darker at birth, particularly in those with white skin, and will become progressively lighter over the next year or two. Very occasionally they may seem to disappear altogether, though this is rare. Nevertheless, a CMN that is regarded as disfiguring at birth may become quite tolerable after a year or two because of this lightening effect.

  The colour may vary a good deal in different parts of a CMN, particularly in larger ones. Darker areas usually indicate that the melanocytes are present there to a greater depth.

  Over the years, there may be a good deal of change. Darker areas or lumps may appear, but these changes rarely need cause medical anxiety. This issue is dealt with in greater detail later.
• texture
  The texture of large CMNs tends to be different from that of normal skin, being softer, looser and more wrinkled. The skin tends to be more fragile than normal, tearing rather easily if traumatised.
• hairiness
  CMNs are usually hairier than normal areas of skin, but this is also very variable. In some cases, the increased hair growth is barely perceptible, whereas, in others, hair may grow profusely from the surface of a CMN. This increased hair growth may not be apparent in the first weeks or months, and tends to increase over the first few years of life. It is probably the result of stimulation of the hair roots (hair follicles) by the cells comprising the CMN.
  The colour of the hair over a CMN is generally darker than the child’s scalp hair. If a CMN is on the scalp, this will usually result in an area of darker, more luxuriant hair growth over the lesion, which may itself be invisible under the hair.
  Paradoxically, occasional CMNs are completely hairless, even ones that occur in the scalp.
• lumpiness
  Smaller CMNs are generally more or less flat, flush with the surrounding normal skin. However, when a CMN is more extensive, it is more frequent for there to be raised or lumpy areas. This doesn’t imply any special medical problem, just that there are larger and deeper collections of melanocytes in these areas. Some lumps are paler and softer than the rest of the CMN, and some are firmer and darker.
• hardness
  Very rarely, a CMN may be really quite hard from the beginning, or may become harder over a period of time. This hardness is usually due to fibrosis, a kind of scarring process, the exact cause of which is unknown. This process is generally accompanied by loss of hair and often also by decreasing pigmentation.
• eczema
  The skin overlying a CMN is often rather dry and itchy, and may sometimes develop frank eczema. This can largely be avoided by regular application of a moisturiser as soon as any dryness becomes apparent. Avoid the use of soap as it tends to dry the skin further. If eczema becomes a problem, you may need to see your GP or speak to a dermatologist.
• underlying absence of fat
  This is something that is generally only seen in the case of larger CMNs, particularly those on the buttocks or limbs. For some reason, the presence of the CMN interferes with the development of the layer of fat that is normally present between the skin and underlying muscle and bone. This can result in the CMN appearing to be depressed below the general skin surface. An affected limb, buttock or side of the face may be obviously thinner than normal. This has no special medical significance other than its aesthetic effect.
• 'satellites'
  

  Many children who have a CMN, particularly when an extensive one, will have smaller pigmented spots elsewhere on the skin. These are known as ‘satellites’. While these can look quite similar to ordinary ‘moles’, they are often bigger. Some may already be present at birth. These will tend to be bigger than those that develop later, which are most often ½ -1 cm across. These larger ones are sometimes hairy and raised. As the child grows, the satellites become progressively, but proportionately, larger.

  Satellites may or may not increase in number over the years, and it is impossible to predict how many are likely to appear in any individual. Their final number may be as many as a few hundred. There is a strong suspicion that exposure to sunlight increases the rate of appearance of new satellites in exposed areas, and this is one of the reasons why anyone with a large CMN should minimise sun exposure.

There are 3 principal health implications of which parents should be aware:

• risk of malignancy
  

  Is there is a risk of malignant tumours in those with a CMN? The medical literature on CMNs has been preoccupied with this issue for many years. There has been a general assumption that large CMNs carry a risk of 5-10% of becoming malignant at some time in the patient’s life. It has also been assumed that the larger the CMN, the greater will be the risk.

  These assumptions are unreliable because they are based on information that was inadequate, both in quality and in quantity. The way this risk has been calculated has been to count up the total number of patients with CMNs who have been seen in a particular hospital, and the number in whom malignant melanoma was thought to have occurred. This method can be expected to produce a much distorted picture of the true situation, because patients are more likely to attend a hospital if they have a serious complication, particularly a suspected malignancy. This effect will automatically inflate the apparent frequency of malignancy in CMNs, as there is likely to have been substantial number of patients with uncomplicated CMNs who did not turn up at the hospital. In countries where patients have to pay to go to a hospital (most countries in the world), they are unlikely to do so unless they can afford to, or are anxious that they may have a serious medical problem that makes seeking medical advice seem a priority.

  Another major problem has been a now well-recognised tendency to over-diagnose malignant melanoma in specimens (biopsies) taken from CMNs, especially from nodules or areas of changing pigmentation. This has also added greatly to the overestimating of the risk of malignant melanoma in the past, and is almost certainly still occasionally a cause of misdiagnosis and unnecessary anxiety today. The correct interpretation of this kind of biopsy is notoriously tricky, and should be undertaken only by those who have the necessary skill and experience.

  I hope that this explanation will help readers to understand why the estimates we have are unreliable. Although it is clear that malignancy definitely is a risk of having a CMN, we really do not know the scale of the risk based on the data currently available, and most experts with experience of care of patients with CMNs believe that the risk is smaller, probably much smaller, than has previously been suggested.

  Large-scale prospective studies of unselected groups of children with CMNs are badly needed. ‘Prospective’ means looking at a problem in a forward direction, rather than retrospectively. Children with ordinary, uncomplicated CMNs need to be identified early in their lives, entered on to a register and then followed up at regular intervals over a period of many years, in order to record just how many develop malignancy. We call such a group of children ‘unselected’. In contrast, a ‘selected’ group means that the individuals taking part in a survey have been chosen for a reason or reasons other than that they simply had a CMN. As we have already considered, it may be that the individuals who are the subject of a survey were actually referred to a hospital precisely because there was a worry that malignancy might already have developed, because - for example - there had been a recent change in their CMN. It is almost invariably the case that in ‘retrospective’ surveys, the patients have been selected in a way that produces a bias in the results of the survey. That bias is of course likely to make the situation look worse than it really is.

  My view is that the risk has been greatly exaggerated in medical books and articles, and that it may be no greater than about 2%, even in large CMNs. This means that perhaps 1-2 persons in 100 with a large CMN will develop a malignant melanoma during their lifetime. The risk for those with small CMNs would be even less clear, maybe none at all. There is an excellent website provided by the US CMN support group known as Nevus Network, where the group publishes the results of surveys of its considerable number of members. Their figures for risk of malignancy among their own members are very low indeed, and very reassuring.

  When considering these risks, you need to bear in mind that every one of us has a risk of about 40% of developing some kind of malignant tumour at some time in our lives. Having a large CMN may therefore only put up the risk from 40% to 42%, which I think you would agree is not a great deal.

  However rarely malignancy may occur in practice, you will naturally be keen to know under exactly what circumstances one should suspect that a malignant melanoma had developed in a person with a CMN. From many years of my own experience and from asking questions of my medical colleagues, I have gained the strong impression that this can be very difficult. Unfortunately, most often it seems to be the case that when malignant melanoma occurs in a person with a CMN, it has usually spread widely internally by the time there is any outward sign of a problem. In such cases, there will generally have been no warning change in the CMN or in any of the satellites, if these are present, and no real indication therefore of where the malignant melanoma started. Unfortunately, once malignant melanoma has spread internally, it is generally impossible to treat effectively.

  The best hope of curing malignant melanoma is when it takes the form of a well-defined nodule appearing within an established CMN, which can be removed surgically before it spreads to internal organs. However, malignant melanoma arising in this way appears to be exceedingly uncommon. Where it does happen, a nodule appears within a CMN and will be noticeable by its rapid growth, and after a few weeks, by ulceration and bleeding. The problem is that new nodules appear in CMNs quite frequently, and the great majority are completely harmless. While it is therefore important to keep an eye on a large CMN for possible malignant change, in practice this may lead to anxiety about every slight change that occurs. In some cases, such anxieties have led to many biopsies being taken for analysis over the years, a process that can be distressing for patient and parents alike.

  As we have already considered, the situation is further complicated by the fact that analysis of this type of biopsy can itself be very difficult. All too often, malignant melanoma is diagnosed when perhaps the lesion biopsied is not truly malignant.

  Out of all this difficulty emerge certain reasonable recommendations. Firstly, you should keep an eye on a large CMN and its satellites. If a new nodule arises within them, you should consider seeking medical advice. You need to remember that the risk of a nodule being malignant melanoma is very low, unless it is enlarging very rapidly, or has ulcerated or bled, in which case the risk will be a little higher. If malignant melanoma is diagnosed, it is worth asking whether a second opinion has been sought on the biopsy from an expert. You will generally find that this is the case, but be aware that even the experts find it difficult to be certain.
• risk of involvement of the brain or spinal cord
  

  Just as a CMN is an abnormal collection of melanocytes in the skin, so can similar accumulations of melanocytes occur in the brain; this situation is called intracranial melanosis. These collections almost invariably occur in combination with CMNs in the skin, and the combination is termed called neurocutaneous melanosis (NCM).

  Intracranial melanosis can interfere with the brain’s function, and the principal problems that may result are fits (convulsions), developmental delay and unsteadiness or clumsiness (ataxia). These problems almost always have their onset during the first 2 years of life, although there may be a life-long risk of neurological complications. In a young child, slow attainment of developmental milestones will provide an important clue. However, the wide variety of possible locations of the accumulations of melanocytes is reflected in an equally wide variety of possible consequences.

  Magnetic resonance imaging (MRI) is a way of looking at internal organs without X-rays. It has proven very helpful in identifying tissues containing melanin pigment. Before MRI became available a few years ago, it was almost impossible to identify intracranial melanosis during a person’s life, and it was only ever diagnosed after death during post-mortem examinations.

  There have now been a limited number of studies to try to establish just how common it is in those with large CMNs, but the results have varied by a surprising amount. Our own studies in London have indicated that while intracranial melanosis is less common than has been suggested in some of the studies, it is nevertheless a relatively frequent finding. In recent years we have scanned about 100 young children who saw us because of a CMN with a diameter greater than 2cm on the head or over the spine. We found evidence of intracranial melanosis in 1 in 10 of these children. We had expected to find that this could occur without the child having any symptoms, but, in fact, almost all the patients in whom these abnormalities were visible on the scan had already developed symptoms, of the type described above, by the age of 18 months. However, we know that symptoms may at least occasionally not occur until later. How great the risk is in those cases in which the child’s CMN occurs at sites other than on the scalp or over the spine is unclear, but we consider that the risk is probably very low. In fact, it looks increasingly as though the presence of satellites is one of the most important indicators of risk, and that intracranial melanosis is relatively rare in children with a single CMN in the absence of satellites.

  Another finding in our study was that 2% of the children we scanned had an abnormality of brain development known as an arachnoid cyst. As it happened these were children who also had intracranial melanosis. Arachnoid cysts are fluid-filled spaces in the brain which may be associated with under-development of certain parts of the brain, and sometimes with hydrocephalus – a situation in which the pressure in the fluid surrounding the brain increases dramatically. This can result in increasing head size, and if severe, with vomiting. If a baby with a CMN on the scalp or back starts to vomit frequently, this should therefore be brought to medical attention fairly urgently.

  Four percent of the children we scanned had tumours in or around the brain or spinal cord. In half the cases (2%) these turned out to be malignant melanomas and in the other half they were apparently unrelated benign tumours, all of which were subsequently successfully removed neurosurgically.

  It is our currently policy to undertake MRI brain scans of all children with hand-sized or larger CMNs on the scalp or on the back close to the midline. We now believe that the best time to do these scans is in the first year of life, because some of the abnormalities can be treated surgically.
• risk of involvement of the eye
  

  Our own experience indicates that when a CMN is very close to an eye, there is a small risk that the eye will develop an abnormality known as glaucoma. Glaucoma means that the pressure of the fluid in the eye is increased, either because of overproduction of the fluid, or because it cannot drain out of the eye in the usual way. It is perhaps most likely that the glaucoma we occasionally see in this situation is due to interference with the drainage process, but the exact reason is unknown. Glaucoma of this type can be treated surgically. It is important to do so as soon as possible after it is recognised because, after a period, the increased pressure can begin to damage the eye permanently. For this reason, it is important to have the pressure in an eye checked when there is a CMN very close to it. Even if the pressure is normal at the time, it will probably be wise to re-check at intervals.

  When a CMN is close to the eye, there may be accumulations of melanocytes in the outer part of the eye, causing darker, often bluish patches over the white areas (the sclera). These almost never have any sinister implications. However, although they may be aesthetically undesirable, they cannot currently be removed.

The majority of CMNs are unsightly. Some are highly disfiguring, and therefore a potential cause of great distress. If CMNs could be completely removed, easily and without trace, there would be little for us to discuss here. Sadly, for the time being, this is not the case.

Before talking in more detail about treatments, it might be helpful for readers to understand more about the skin, and about the way it heals after injury. This requires a basic knowledge of the way the skin is constructed.

The skin has 3 principal layers, the epidermis on the outside surface, the dermis immediately below it, and a layer of fat below that, known as the subcutaneous fat.

Epidermis.

The main functions of the skin are to protect the body from loss of fluid, and from entry of micro-organisms and noxious substances. These functions are mainly the responsibility of the stratum corneum, whose manufacture is the reason for the existence of the epidermis.

The stratum corneum is made of closely packed cells, known as keratinocytes, which are produced by the lowermost cells in the epidermis, the basal cells. The basal cells form a continuous layer (the basal layer), immediately above the dermis. The cells of the stratum corneum are created by repeated division of the basal cells. Following this, they gradually mature into stratum corneum cells during their outward passage through the epidermis. As they mature, they are continually pushed outwards by successive generations of cells until they reach the surface.

In reality, the epidermis is not simply a thin, flat layer like paint on a car, but a more complex structure with parts that penetrate more deeply. The parts that penetrate most deeply are the hair follicles and sweat glands.

The hair follicles are the structures from which individual hairs grow. They are deep extensions of the epidermis, and hair is made, like the stratum corneum, by keratinocytes. Because the hair follicles penetrate so deeply into the underlying dermis, they have the ability to provide basal cells to help with healing after an injury that removes more superficial parts of the basal layer.

Dermis.

The dermis is a physically strong and resilient foundation for the epidermis, containing all the services that the epidermis requires to function. The dermis contains collagen which provides the skin with its great flexibility. Elastic fibres are also present and allow some stretching. Between these fibres run the blood vessels that nourish the epidermis, as well as its supply of nerves.

Subcutaneous fat.

Under the dermis is a layer of fat. This fat has a number of functions other than its principal one, of storing nourishment. It provides protection against heat loss from the muscles, which have a high blood supply, and is important aesthetically in conferring a smooth contour to the skin.

Under the fat are the muscles, separated from it by a thin layer called fascia.

Surgical excision: basic principles

Having considered the basic construction of the skin, this is a good point to consider the basic principles of surgical removal (excision) of skin lesions.

When skin is damaged to such a depth that some of the basal layer is lost, repair occurs by means of basal layer cells from neighbouring epidermis spreading out on to the damaged surface where they start to produce new keratinocytes. This spreading out takes place from the nearest site at which these basal layer cells remain intact, which will include hair follicles and sweat glands. Clearly, the basal layer cells cannot travel very far very quickly.

As we have considered earlier, the cells in a CMN are melanocytes and melanocyte precursor cells, present in very large numbers at sites in the skin where they would normally not be found. The more extensive the CMN, the lumpier and the hairier it will tend to be, and the greater the depth to which these cells will be situated. The cells may extend though the full thickness of the dermis and even through the subcutaneous fat, to the level of the fascia. They do not enter the underlying muscle.

To remove a large CMN completely will usually require full thickness removal of the skin, including the subcutaneous fat. However, only a small proportion of the cells within the CMN are actively producing pigment, and these will be those situated fairly close to the surface, immediately below the epidermis. The more deeply situated cells tend not to produce pigment and have a different appearance when viewed under the microscope. These cells are not actually melanocytes at all, but develop from the same precursor cells as melanocytes. These cells often look very much like nerve cells under the microscope, and appearance that is technically termed ‘neuroid’. This can lead to misinterpretation if the person examining the material is not fully aware of its nature. As a result, some children or adults have mistakenly been considered to have neurofibromatosis following a biopsy from a CMN.

Full-thickness surgical excision will involve loss of all sources of basal layer cells within the treated area, and therefore the only remaining source of such cells to initiate healing will be from the edges of the wound. Healing from the edges of a large full-thickness wound would take so long that infection and other complications would be invariable, and the quality of the wound would be very poor indeed, even if the person survived. Therefore, full-thickness excision of skin requires the wound to be closed, either by bringing the edges together in some way, or by moving in skin from some other site to cover the denuded area.

Partial-thickness surgical excision will, on the other hand, heal quickly, because there will be plenty of remaining hair follicles and sweat glands, which can provide basal layer cells to repopulate the area of loss. This is the way a graze heals.

Full thickness excision

To remove all the melanocytes in a CMN will invariably mean excision, as defined above. This would remove the pigmentation, the extra hair growth and the abnormal skin texture at the same time. The defect left in the skin will need to be closed; how this can be achieved requires further explanation.

Full thickness excision is the most certain way of removing a CMN, and is relatively straightforward for removing small lesions, as the wounds can be stitched up directly. If the CMN is a little bit too large to be removed at one go, it can often be removed in two stages. This is called serial excision.

If a CMN is even more extensive, its removal would leave a defect which cannot simply be repaired by stitching it up. Such holes can be closed in one of three ways (or by a combination of these), by grafting, by rotation flaps, or by tissue expansion.

Whatever method is used to close the defect left when a CMN is excised, there will be a risk of pigmentation appearing at the edges of the site of the excised CMN. This is known as the ‘tide-mark’ effect.

Grafting

The simplest way of repairing a large defect is with a skin graft. Most skin grafts are of partial thickness, and are taken from a ‘donor’ site somewhere else in the body, usually - for convenience - the thighs. After the donor site has healed, it may be left with some change in pigmentation and – occasionally - scarring. When the graft is placed in the gap left by the removed CMN, it will heal but there will be a net loss of bulk as the thick CMN is being replaced by a very thin skin graft. In addition, the surface will tend to look scarred, like a burn. It will be hairless and rather shiny, and experience has shown that appearance of spotty repigmentation is almost invariable. A graft will not grow in proportion to a child’s own growth. This can cause problems if the graft crosses a joint, as the mobility of the joint will be compromised. This can usually be corrected by a further operation to insert an extra graft, but it is usually best to avoid grafting over joints if this is possible.

Skin grafts can be used to remove very large areas of CMN, but there is usually too little donor skin available to do more than a relatively small area at a time, using the same donor site on each occasion.

One can use full-thickness skin grafts in some situations. These can give a very good result, but they can only be small; otherwise the donor site will not heal. They will be reserved for important sites, usually on the face. Small full-thickness grafts are usually taken from behind the ear or in the groin, where the skin can be stitched up to give a straight line scar. Sometimes larger areas are used, in which case the donor site will have to be closed with a partial thickness graft from elsewhere.

The main problem with grafts is that they don’t always ‘take’ as well as one would wish, and the final aesthetic appearance will then be less satisfactory. Even when they take well, skin grafted with partial thickness grafts will tend to look unsightly. For this reason, grafting is generally best avoided in cases where excision is undertaken primarily on aesthetic grounds.

Tissue expansion is a technique in which the area of skin available to close a defect is increased by prior stretching of the normal skin around the site at which an excision is planned. The stretched skin is (technically) of full thickness, and will have some of its underlying fat, and it will have a colour and texture appropriate to the site where it will be used. Usually this stretching is achieved over a period of weeks. The first stage is the insertion (which requires a general anaesthetic) of a silicone balloon (tissue expander) just beneath the skin. The balloon is attached, via a small tube, to a filler port. This port is also under the skin, and the balloon can be filled progressively by injecting it with small volumes of saline (salt water) every few days. The injections can be undertaken by a nurse or by parents. It generally takes 6-8 weeks to fill the balloon adequately. Removal of the CMN can now be scheduled, and the balloon will be removed during the operation.

This technique is only suitable for certain sites. We use it as first choice for the head and neck, often also for the trunk where the CMN is not too large, but less frequently for the limbs. The skill is to expand the right area of skin, and then to move it in to replace the CMN with the minimum of scarring. Sometimes, if the CMN is large, two or three tissue expanders may be used at the same time. It may also be necessary to repeat the whole process on more than one occasion.

The swelling that is visible while the balloon is in place can prove an aesthetic problem in adults and in adolescents, but rarely bothers younger children.

There is a small but real risk that the tissues around the balloon will become infected, which will usually mean that the balloon will have to be removed.

Occasionally, the stretching is too great for the skin to cope with, and it breaks down.

Where the amount of extra skin required is not great, the expansion can sometimes be done quickly during the operation itself (‘intra-operative’ tissue expansion).

Rotation and transposition flap. A rotation flap is an area of full-thickness skin that is lifted off the underlying tissues, and moved - with its blood vessels still connected - to fill a defect in an adjacent area. It is rather difficult to describe exactly how this is done, but whether it is an option depends very much on the site. The scalp and the face are good sites for this technique.

A transposition flap is similar, but in this case, an area of full thickness skin, often also including fat, is moved to a distant site where the blood vessels are re-connected.

The main advantage of these techniques over grafting is the excellent final quality of the re-located skin, and the advantage over tissue expansion is that no additional operations are required, nor the long period of balloon-filling. In practice, these days, the most favoured techniques for removal of CMNs are excision with direct closure or tissue expansion, or serial excision with direct closure or tissue expansion.

Partial thickness removal

As considered above, the cells in a CMN that are actively producing pigment are generally those that are fairly close to the surface. It is therefore tempting to take advantage of this and just to remove these cells, leaving the majority of deeper, non-pigment-producing cells alone. This type of approach can be aesthetically useful on occasions, but in the longer term, the melanocytes that have been left behind can themselves start to produce pigment. The benefit of such procedures is therefore often only temporary.

Because the pigment-producing cells are those immediately below the epidermis, one can remove all or most of them by partial thickness excision of the skin, without fully removing the whole CMN. Healing should be quick, as in a graze, generally within 10 days, without requiring any of the techniques described above. As well as removing the pigment-producing cells at the surface of the CMN, it seems that the healed skin overlying what remains may be more opaque than normal, and therefore able to some extent to conceal any remaining pigmentation.

Several different techniques may be used to achieve this partial thickness (‘superficial’) removal. The most traditional is dermabrasion, in which abrasion is used to scour away the surface of the skin. As you can imagine, this is a bit messy. In another technique, called shaving, a thin layer of skin is removed with a special blade called a dermatome - the same type of blade that is used to take skin grafts. Another technique is to use a curette, an instrument that resembles a very small spoon with a sharpened edge, which can be used to scoop out bits of skin. Chemicals such as trichloro-acetic acid have also been used to burn off the surface of the skin (chemical peeling). ‘Resurfacing’ lasers are gradually becoming a popular instrument for superficial removal, particularly the carbon dioxide laser. Like dermabrasion and the curette, lasers allow control of the depth of removal, which will vary in different parts of the CMN. Lasers also have the great advantage of causing less bleeding. The treated site will generally be painful and oozy for a few days afterwards, whichever technique is used.

The results of superficial removal are very variable, and difficult to predict before the operation is performed. The treated area may look good initially, but later on new pigmentation often appears around the edges, (the ‘tide-mark’ effect that I mentioned earlier), and spotty pigmentation frequently re-appears in the treated area. This re-pigmentation may increase for many years and can be substantial. A further disadvantage is that superficial removal will not deal with hairiness, because the hair follicles are not removed. Another problem that can occur is scarring. The occurrence of scars will indicate that the removal of tissue has been too deep in those areas, but often this has happened because the surgeon has simply removed pigment as deeply as it can be seen to extend in a genuine attempt to achieve the best possible aesthetic effect. The scarring that frequently occurs after superficial removal of CMNs tends to improve a great deal over a period of many years, and in fact, the best long term benefit from this type of surgery is often seen in areas that were initially scarred.

There is a widespread belief that the success of this type of procedure depends on the surgery being undertaken very early. There is little evidence that it has to be done in the first few days of life, as is often advocated, whereas there are many reasons for it being more hazardous at this age. My own, unsubstantiated impression is that the results of this type of procedure are likely to be best when it is undertaken within the first 2 years rather than later.

However, I must confess that I have personally become increasingly dubious about the value of these techniques because, in many cases, the long-term benefits are questionable and because the unwanted effects can be substantial. There can be no question that the treated areas are painful until they heal, and that these raw areas are at risk of infection. Although it seems rare, there must be a risk of serious infection including septicaemia, infection of the blood that is potentially lethal, particularly in the very young. Any degree of infection will delay healing, and some areas are probably slow to heal because of unintentionally excessive depth of removal of tissue. Blood loss during the surgery may be considerable, and can be hazardous in the very young.

Laser treatments

Earlier, I considered the use of ‘resurfacing’ lasers which remove layers of skin, such as the carbon dioxide laser, for the superficial removal of CMNs. Other types of lasers are being developed all the time, including ones that target pigment in particular. However, to date none of the types of laser that are currently available have been able to provide consistent results in terms of improving the appearance of CMNs, and I do not feel able to recommend any of them. It is however very likely that new and more effective lasers will be developed, and this is an exciting prospect for treatment of CMNs in the not-too-distant future. For the time being, perhaps the most immediately promising area for the use of lasers in CMNs is for semi-permanent hair removal, ideally left until the multiple treatments required can be tolerated under local rather than general anaesthesia.

As we have already discussed, the risk of malignancy developing in a CMN is already very low and is almost certainly not made any lower by any kind of treatment, including full-depth removal. There is absolutely no justification in seeking excision of a CMN if the purpose is to reduce the perceived malignancy risk. The only purpose of treatment is aesthetic improvement.

In the case of superficial (partial thickness) removal, it appears that the results are only really likely to be worthwhile if the surgery is done in the first months of life, for reasons that are completely unclear. However, as I said earlier, this procedure is very uncomfortable and potentially risky, and because the results are not that good, I no longer feel that it is in a child’s best interests.

In the case of full thickness excision, where treatment is for really significant disfigurement and in a situation where it is likely to provide a substantial aesthetic improvement, an argument can be made for an early start. This situation will mostly relate to highly visible lesions on the face. There are several reasons for preferring an early start to treatment in such cases. For example, the skin is looser in many areas of the body in the very young, making it relatively easier to close after removing a CMN. The psychological impact of surgery is probably also less in the very young. It seems to me that, where possible, one should aim to complete treatment before school age.

However, we are now increasingly taking the view that where lesions are in less aesthetically sensitive areas, particularly on the trunk and limbs, surgical treatments should perhaps be deferred until children are able to decide for themselves whether they believe that an intervention is likely to be a good deal for them.

No, definitely not. Good dermatologists and plastic surgeons will be able to tell you what can be done, and what the pro’s and con’s of particular procedures will be, but it is you as parents who will have to make the decision, on behalf of your child, whether to embark on any of these treatments, and which. And, of course, this decision is made more difficult by the fact that the outcome of a particular surgical procedure is always going to be unpredictable in the individual case.

It is important not to feel rushed into making such important decisions. Treatment is never so urgent that you need to decide immediately. Do not hesitate to seek a second opinion; this is a principle accepted within the NHS. You may find it helpful to meet other parents whose children have had operations similar to those being offered to your child, and it is often possible for support groups to arrange contacts between parents.

The view is gaining strength that – except in the most disfiguring facial lesions – it is right to defer treatment decisions until children are able to express their own opinion. There has undoubtedly been an increasing acceptance among people in general of those born with aesthetically compromising lesions such as CMNs, and it seems likely that the situation will improve further. This means that members of the next generation may not be as bothered by a birthmark as members of this one.

However, in the case of the major disfigurement that may result from a facial lesion, it is not only reasonable but probably responsible of parents to give their child the benefit of earlier treatment.

In considering these matters, it is worth being aware that children rarely experience troublesome prejudice in terms of birthmarks until they are about 10 years old. In practice, it turns out that children may be subjected to dreadful teasing during adolescence, even when they have no real problem at all with their appearance. I have read articles in which some of the best-looking women in the world tell of their merciless persecution as teenagers, because they were considered too beautiful by other girls. What probably matters most is, firstly, one’s personality - whether one is vulnerable to teasing or not - and, secondly, one’s upbringing – whether one was made to feel normal or imperfect in the family situation. We can do little about a child’s personality, but we can, as parents and family friends, do a lot about the second. It would be good if more professional psychological support were available through the NHS to support children with significant CMNs through later childhood and adolescence, but currently there is not anywhere near what is needed. The Birthmark Support Group is working towards providing help by young adults who have CMNs, and this is in my view an exciting development.

The fact is that currently available treatments are to a great extent unsatisfactory. The results of superficial removal are not statistically that good in the longer term, and the discomfort and dangers of the treatment in the short term are very real. Full depth excision can never be achieved without at least some degree of scarring, and is simply not feasible for most of the largest CMNs. On the other hand, results of full depth excision may be excellent for certain lesions on the face, and at this site, a CMN just a few centimetres across may represent a substantial aesthetic problem. Lesions in the scalp rarely need to be touched as they will usually be well concealed by hair. Very occasionally, scalp CMNs are hairless, and in these cases, excision may be worth considering.

In summary, I feel that there is a strong case to be made for avoiding treatment altogether in many cases, because of the often unsatisfactory nature of the treatments currently available, because of the significant natural improvement that can be anticipated in the colour of CMNs, and because of the increasing acceptance by people in general of those with birthmarks.

We are always hopeful that more effective treatments will become available in the future, including new lasers. For the time being, it seems to me a pity to risk treatment that may itself result in a degree of disfigurement if a child could possibly enjoy the benefit of a better treatment being developed in his or her own lifetime.

For some reason or another, satellites do not appear to be very responsive to superficial removal, and the only satisfactory method is to cut them out altogether. This may be worthwhile for a small number of these lesions, but if it is envisaged that large numbers will be removed, the appearance of the scarring that will result will almost certainly be unacceptable.

Dealing with the hairiness of CMNs is difficult as hair follicles are situated very deeply in the skin. Superficial removal techniques have little effect on this aspect of CMNs and the only absolutely reliable way to remove the hair is to excise the skin and the naevus completely.

Electrolysis is a slow and laborious process and is therefore not suitable for large areas. It is also usually too uncomfortable for children to tolerate.

Parents have the option of shaving the hair regularly. Contrary to popular prejudice, shaving does not affect the amount or thickness of hairs that grow subsequently. Hair regrowth after shaving is generally slow, and the new hairs will have exactly the same appearance and feel as the original ones. Most parents find that they do not need to shave an area more often than once every few weeks in order to maintain a satisfactory appearance. Depilatory creams can be used for the same purpose, but they can irritate the skin. Facial hair removal creams have the lowest potential for irritation and are therefore preferable. Shaving is often the best approach. An electric shaver is probably best, and the models designed for use on women’s legs are probably best of all.

I have already mentioned laser hair removal. Regular treatment over a relatively long period might prove able to provide semi-permanent hair removal in many cases. However, this should probably not be considered until a person is able to have the procedure undertaken with local anaesthesia alone, usually a cream, and this is not likely to be the case until adolescence at the earliest.

Children with large CMNs can and should enjoy as normal a life as possible.

The need for sun protection is worth discussing. There is very little to suggest that special procedures for protecting CMNs themselves from sun exposure are beneficial. Whether parents should take special precautions to protect a child with a CMN from sun exposure more generally is something to consider. We have already considered the question of malignancy risk in a CMN, and it appears that there is relatively little. However, you will be aware that there is now plenty of evidence to indicate that pale skin that becomes red after sun exposure and tans reluctantly is a risk factor for development of malignant melanoma. So also, it seems, is an abundance of standard-type moles. It seems possible, indeed likely perhaps, that the presence of a large CMN might also indicate a risk, not in the CMN itself but in apparently normal areas of skin. While there is no strong evidence available, I am anxious that this may be true at least in those who have large numbers of satellites. We know that many children in this category will continue to develop new satellites during their childhood, and that sun exposure seems to encourage this. It seems logical to worry that in such cases, at least, there may be a slightly increased risk of melanoma in the whole skin. If this were true, reasonable levels of sun protection would be a logical precaution.

With this in mind, let’s look at what might be considered to be reasonable levels of sun protection. We know that the greatest risk factor for malignant melanoma is sunburn, and this therefore has to be has to be avoided especially. The presence of the sun is a fact of life, and complete avoidance of exposure of any part of the skin at any time is an impossibility. Therefore one has to achieve a compromise. When considering this subject, you should bear the following general rules in mind:

• The sun is most harmful during the months April to October, inclusive.
• On a daily basis, the sun is most harmful during the hours 10am-4pm, inclusive.
• Exposure is increased greatly by reflection when beside water or snow.
• The sun is more harmful at higher altitudes.
• The sun remains almost as harmful in cloudy conditions.
• The best protection is clothing, which is most protective when darkly coloured.
• Shade (including hats) provides some protection, but less when near water or snow or when the weather is cloudy.
• Sunscreens are merely a last and at best, partial barrier, and are not a substitute for other forms of protection.
• The best sunscreens contain a reflectant barrier such as titanium dioxide; select a high protection factor (SPF), ideally 25 or greater.
• Sunscreen needs to be refreshed every 2 hours or so, more often when swimming or sweating.

Skin care of CMN's

The skin over a CMN tends to be rather fragile and therefore easily torn if traumatised. It is usually also dry and therefore very prone to develop eczema. This dryness and predisposition to eczema will tend to be worse during the winter months. It follows that good care needs to be taken of the surface of a CMN to maintain optimal skin condition and minimise problems. Soap should be avoided at all times, and the surface should be cleaned by applying a bland water-dispersible cream as if it were soap during a daily bath or shower. Suitable creams that can be bought across the counter in a chemist, or prescribed, include Cetraben™ cream and Diprobase™ cream. If the surface remains dry despite this, the same type of cream should be applied as a moisturiser at other times, as often as is necessary. Itchiness of the surface means that eczema is developing, in which case a mild topical steroid preparation may be required to bring the situation under control. Dealing with this type of eczema is not normally difficult once the problem is recognised.

Psychological issues

Children who grow up with a prominent CMN and/or satellites may well have problems adjusting to the disfigurement that they perceive, particularly during the years of adolescence. This will vary greatly for different children, depending largely on their own personality and on the support they have enjoyed from family and friends.

As we considered earlier, it would be ideal if we were able to offer all children at risk some degree of automatic counselling during their childhood, but currently the resources are simply not available for this. Additional help can now be obtained through the Birthmark Support Group. In addition, there are some organisations specifically dedicated to disfigurement issues, and they are well worth approaching on this subject. Changing Faces is an example of an support group specialising in disfigurement; click here to go to their website.

CMNs appear to be largely ‘one-off’ events, and not inherited. The risk to any further children of a couple who already have a child with a CMN is very small. Similarly, the risk of a person with a CMN themselves having a child with one is very small.

Parents of children with CMNs are eligible for this benefit if they are spending more time on their child’s care than would be the case for a normal child. The calculation includes time spent on skin care and hospital visits. If you would like further advice, contact your Citizen’s Advice Bureau or the Social Services Dept. in any hospital your child visits.