Giant congenital melanocytic nevi are large, dark-colored lesions on the skin. They’re generally not harmful but may increase your risk of conditions like melanoma. Treatments are available.
A giant congenital melanocytic nevus (GCMN) is a rare, substantially sized dark lesion that appears on the skin at or around birth. Giant-size nevi begin at or grow to more than 40 centimeters (15.75 inches) across by adulthood.
GCMNs are generally not harmful, but they do indicate an increased risk of some serious health conditions. Depending on their location on the body, they can also cause psychological distress. GCMNs require regular monitoring by a doctor.
Treatments can include management and removal or reduction. You may also seek psychological support if needed.
GCMNs appear differently on each person, but they will be substantial in size. They may appear:
- as flat lesions that can become raised or thickened over time
- tan or another shade of brown that can darken or lighten with time
- with irregular borders
- rough or nodular surfaces
- with satellite nevi (additional smaller nevi)
GCMNs can appear anywhere on the skin but
Nevus size and related conditions
GCMNs grow to larger than
A large or giant nevus may carry a 5% to 10% risk of becoming cancerous over a person’s lifetime, though that may be an overestimate.
Neurocutaneous melanosis affects the central nervous system and can cause seizures, delayed development, and cranial nerve dysfunction, among other symptoms.
Classifying nevus size
Doctors classify nevi according to their
| Category | Diameter |
|---|---|
| small | less than 1.5 cm |
| medium | 1.5 to 20 cm |
| large | 20 to 40 cm |
| giant | more than 40 cm |
A GCMN may have no symptoms, or you may experience symptoms such as:
- skin sensitivity
- itchiness
- skin fragility
Talk with a doctor if you observe any sudden changes to the GCMN and surrounding skin. Changes in the size, color, and thickness of a GCMN are expected but still require regular monitoring.
Have a doctor immediately examine any pain, bleeding, and other significant changes to the nevi and surrounding area.
Gene mutations that occur in the womb cause GCMNs. These mutations
The gene mutations cause an overproduction of melanocytes. Melanocytes are the cells responsible for producing melanin, the substance that gives your skin pigment (color).
Genetic mutations are sometimes inherited, meaning parents pass them down to their children. However, the mutations that cause GCMNs are
A doctor diagnoses a nevus based on its size and classifies it as small, medium, large, or giant. They can diagnose a GCMN with a physical exam and dermatoscope, a tool that allows them to look more closely at the skin. If they suspect melanoma, they may wish to take a biopsy.
Experts also recommend that doctors order an MRI scan within
A doctor may refer you to a specialist, such as a dermatologist or plastic surgeon, based on findings from the exam.
Treatments for GCMNs vary from person to person. Many factors can determine treatments, including the size and location of the nevus, and the risk of more serious health conditions like cancer or neurocutaneous melanosis.
Treatments may include:
- regular management
- cosmetic removal or reduction
- prophylactic (preventive) surgery
- psychological support
There’s no one-size-fits-all approach to treating a GCMN. You can discuss treatment options with a doctor to determine how to manage the GCMN considering both the physical and emotional factors involved.
Monitoring and management
Your doctor will want to monitor a GCMN annually or more often, particularly in infants.
Regular care of the nevi may include sun protection, such as using sunscreen and wearing protective clothing to limit sun exposure.
Cosmetic removal or reduction
Surgical removal of the GCMN is only necessary if it becomes malignant (cancerous). However, a doctor may recommend a treatment plan that removes or reduces the size or color of the GCMN. Options include:
- dermabrasion to remove part of the GCMN
- shave excision to remove the top layer of skin
- chemical peel or laser ablation to lighten the appearance of the GCMN
- laser therapy to remove the GCMN
Removing or reducing GCMNs may be complex. The process may take time and several procedures. Wound closures could involve skin grafts or tissue expansion.
However, these treatments
Prophylactic (preventive) surgery
A doctor may recommend surgery to remove a GCMN if they believe the risk of complications is very high. This involves surgical excision of the lesion followed by some reconstruction.
However, removing the GCMN doesn’t entirely eliminate the risk of melanoma. About half of the melanomas that develop in people with GCMNs occur elsewhere in the body. Some are even extracutaneous, meaning they don’t affect skin.
Read more: “What Are the Types of Melanoma?”
Psychological supports
Living with a GCMN may take a toll on your mental and emotional health. In a
- anxiety
- depression
- aggressive behavior
- social difficulties
A doctor may recommend treatments such as therapy or support groups, or you may seek similar options for yourself.
If you have a GCMN, regular checkups with a doctor to monitor for unusual changes can help you manage your risk of complications like melanoma or NCM. A doctor can also help evaluate your overall well-being and recommend treatment plans that consider your cosmetic and emotional needs.
For those without complications, a GCMN may not affect their life expectancy much. However, for those who develop melanoma or neurocutaneous melanosis, survival rates are often low.
Melanomas from GCMNs tend to develop by
Neurocutaneous melanosis also has a negative effect on outcomes in people with GCMNs. Most babies with neurocutaneous melanosis die within
Is congenital melanocytic nevus harmful?
GCMNs can be harmful because they may be associated with serious health conditions like cancer and neurocutaneous melanosis, which occurs in about
The condition can make you susceptible to psychological distress, which may be harmful to your outlook. Talking with a therapist or finding a support group may improve your sense of self if you live with a GCMN.
Should you remove a melanocytic nevus?
Doctors debate whether there’s much benefit to removing a GCMN. Advocates for removal argue that melanoma rates are lower among those who have had surgical removal. Others argue that the risks of surgery may outweigh the low risk of melanoma, and that surgery doesn’t completely remove the risk of melanoma anyway.
Currently, the
You can discuss options for removing GCMNs with your doctor. Removal methods will vary depending on the size and location of the GCMN and whether it affects other parts of your body.
Do congenital melanocytic nevi go away?
GCMNs do not go away, but their appearance could change over time.
GCMNs appear at birth or in infancy and stay with you throughout your life. They may grow and change over time, and they require regular monitoring by a doctor.
Treatment plans may include removal or reduction as well as psychological support. Talk with a doctor about your options or if you notice any significant changes to the GCMN.