Frequently Asked Questions

Here are the answers to the questions we get asked the most about large congenital melanocytic nevi. This text is available from Nevus Outreach in the form of a handy brochure. Fill out this form and we will send you our information packet.

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What is a congenital melanocytic nevus?

Nevus (also spelled naevus; plural nevi) in the broad sense, means birthmark. There are several types of nevi: epidermal, melanocytic and connective tissue nevi. Melanocytic means that it is pigment-based. Congenital means it is present at birth. Nevus Outreach deals with large and giant congenital melanocytic nevi.

Nevi are the most common abnormality of the skin. They apparently serve no function. Normally, skin gets its color from melanin, which is produced by cells called melanocytes. Melanin is human pigment. Normally, melanin is distributed fairly evenly throughout the skin. Congenital melanocytic nevi, on the other hand, are made up of pigment-producing cells called nevomelanocytes. These cells are not evenly distributed. When many nevomelanocytes are clumped together, they can result in moles on the skin because of the higher concentration of melanin (pigment).

How are nevi measured?

Since nevi can be found on any part of the body, and grow as the body grows, the term large can be difficult to define. Doctors don’t all use the same definitions. Here are the most common ones - a doctor may use any of these in defining the size of a nevus.

A nevus may be described as large if:

• It would take more than one surgical excision to remove. Surgeons and others involved with the removal of nevi, sometimes use this definition.

• It covers more than 2% of the patient’s total body surface area, or is larger than the palm of the patient’s hand.

• It measures over 8” (20cm) at its largest point on a fully-grown adult. When applying this definition to a newborn or child, the nevus is large if it is expected to be this size by adulthood. For example, a 3” (7cm) lesion on the head or a 2” (5cm) lesion elsewhere, noted at birth, will grow to be at least 8” by adulthood. Therefore these would be considered large nevi at birth.

• It covers a large portion of a major anatomical site. Thus, nevi on the head, legs or arms may be categorized as large even if they do not meet the previous definitions.

The term giant is sometimes used when describing nevi. A giant nevus covers a very large part of the body, usually involves the torso, and is usually accompanied by a number of satellite nevi. Satellite nevi (or just satellites) are smaller melanocytic nevi. When a child is born with a giant nevus, it is common for satellite nevi to be present at birth. It is also common for satellite nevi to appear after birth. Sometimes during diagnosis, doctors may use a large number of satellites to support their diagnosis of a large or giant congenital melanocytic nevus.

How common are congenital nevi?

Small melanocytic nevi are very common. One in every 50 to 100 people is born with a small melanocytic nevus. Large congenital nevi occur approximately once in every 20,000 births. Giant congenital nevi are thought to occur approximately once in every 500,000 births.

How is nevus-skin different?

Nevi are much more than simply dark skin. Besides producing increased pigmentation, the area covered by a melanocytic nevus often produces increased amounts of hair. The formation of sweat glands can be disrupted in nevi – so sometimes a person with a large nevus may not sweat where their nevus is located. Many nevi lack subcutaneous fat, a layer of fat just under the skin that pads the body everywhere. Some nevi will also have neurofibromas or other neural tumors, within their borders. These growths are not painful and are normally superficial. Nevus-skin can range from thick with a folded appearance, to thin and fragile. People with nevi sometimes complain that their nevus itches more often than the surrounding skin.

What causes nevi?

Large congenital nevi form in the womb very early in development, within the first twelve weeks of pregnancy. They are caused by a defect during embryologic development. There is no known method of prevention. They appear in either sex, in all races, and on any areas of the skin.

What doesn’t cause nevi?

At Nevus Outreach, we frequently hear from new parents wondering what they must have done to cause their baby to be born with a large nevus. It is important to know the difference between congenital and hereditary. Congenital means present at birth and nothing more. Hereditary means you get if from your parents and/or pass it along to your kids. There is no evidence that congenital nevi are hereditary. We know of cases of identical twins, where one child has a large nevus and the other does not. We know of no cases where identical twins both have a large nevus. We know of no cases where a person with a giant nevus has either a parent or a child who also has one. We know of no cases where alcohol, drugs, diet, illness, injury or any other external factor for a parent can be linked to the formation of a large nevus in their child. If you are the parent of a newborn with a large nevus and you think you caused it, there is no evidence to support that. You did not cause it.

Can nevi pose a health problem?

Having a large nevus can impact one’s mental health. Large nevi are obvious and unusual. These can be difficult hurdles to overcome.

In terms of physical health, pigmented moles have been linked to melanoma, a potentially deadly skin cancer. Also, certain children with large nevi may have melanin, melanocytes and/or nevomelanocytes in their central nervous systems (the brain and spinal cord). This condition is known as neurocutaneous melanocytosis (melanosis) (NCM). Most people with NCM do not have neurological problems. However, some do, and the complications from NCM can be very serious.

Which moles may develop melanoma?

Scientific opinions vary as to the exact risk of melanoma, but current research may show the number of children born with large nevi who develop melanoma later in life to be around 5%. Any congenital nevus, small or large, may develop melanoma, but those of greatest concern are very large or thick. Studies indicate that satellite nevi rarely, if ever, develop melanoma.

What are the signs of melanoma?

Changes in size, color, surface texture, pain, bleeding, or itching are all of concern. Any such changes should be evaluated medically if they last longer than two weeks. Additionally, the presence of a lump which you can feel under a large congenital nevus may be of concern, since melanoma may arise deeper in a larger nevus. If melanoma is suspected, usually a small sample of the mole is removed and sent to a pathologist for diagnosis.

What should be done about a congenital nevus?

Because of the rarity of this condition as well as the lack of understanding of large nevi among doctors, there is a wide range of professional opinion regarding how to treat large congenital nevi. However, there is a reasonable consensus on the first few diagnostic steps. Work closely with your doctor, who may refer you to a dermatologist specializing in pigmented skin lesions. Where NCM is suspected, you may be referred to a neurologist. These evaluations may lead to other tests such as a skin biopsy and/or an MRI.

In many cases, surgical removal of large nevi may be an option. Treatment is highly individualized and depends on the age and health of the patient, as well as the size, location, appearance, and growth history of the nevus. While most plastic surgeons are trained in the techniques for removal of nevi, their approaches and proficiencies with respect to a particular nevus can vary widely.

“Observation only” (no treatment or removal) is an option chosen by many parents to be in the best interest of their child.

What methods of removal are available?

Small nevi can be removed by simple surgical excision. The nevus is cut out, and the adjacent skin stitched together leaving a small scar.

Removal of large nevi requires replacement of skin in one way or another. These procedures are major surgeries, and require use of general anesthesia. 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). At the time of this writing, laser procedures have not been shown to be effective for nevus removal. There is no known way to remove a nevus that is scar free, but scarring may be minimized at the hands of a highly skilled, experienced surgeon. Removal of very large nevi is typically accomplished by performing multiple surgical excisions over time.

There are also techniques that do not remove nevi but can sometimes provide benefit. Chemical peels can be used to lighten nevi with varying success. Lasers can also be used to lighten nevi, and to remove hair from a nevus. It is unknown whether laser treatments reduce melanoma risk and, in addition, the cosmetic results are unpredictable.

Treatment varies on a case-by-case basis. Different doctors may have different preferences for treatment of a nevus. You should consult your doctor to find out about specific options for you, but remember, most doctors don’t have a lot of experience with large nevi. Don’t hesitate to seek a second opinion. Try to locate a doctor who has experience working with large nevi.

Why remove a nevus?

Most of the time, the overriding reasons to remove a nevus are first to reduce melanoma risk and second to improve appearance which can be fundamental to improving a patient’s overall psychosocial state. Other reasons to remove a nevus may be to improve the strength, texture, sensation, and sweat gland activity of the affected area.

While it is almost impossible to remove every cell of a large nevus, the goal is to remove as many cells as possible while at the same time preserving function and minimizing scarring. Remember, a nevus cannot be removed without leaving a scar.

Some people choose to leave their nevi intact, while others choose to remove them. There are good reasons for both choices. It is a highly personal decision.

How often should individuals with congenital nevi be examined?

Like all moles, large nevi should be examined regularly by a physician. A mole’s color may stay the same, lighten slowly, or darken slowly over time. Hair in a mole is not an indication of malignancy or benignity. On the other hand, any rapid or persistent change in color, texture, or outline, or the development of a new nodule, is cause for immediate examination by your doctor. If scars are present they should be examined visually for pigment recurrence and should also be palpated so as to help detect growths that may develop under the top layer of the skin.