Definition

Nevus pigmentosus (plural: nevi) is the medical term for moles. This nevus consists of clusters of benign melanocytes (skin pigment cells) and is a common skin condition. Nevus pigmentosus is one of several types of nevus. Other names for nevus pigmentosus include melanocytic nevus and nevoid nevus.

Nevus pigmentosus can be present at birth (congenital nevus) or develop at a certain age (acquired nevus). There are several types of congenital nevus and acquired nevus.

Causes

The precise cause of the local proliferation of melanocytes leading to the formation of a nevus remains unclear. However, it is evident that the number of nevi pigments an individual has depends on genetic factors, sun exposure, and immune status. This can be explained by the following:

• Individuals with numerous nevus pigmentosus often have family members who share the same condition.
• In congenital nevus pigmentosus, mutations or abnormalities in specific genes have been demonstrated.
• Medications such as vemurafenib, dabrafenib, and immunosuppressive agents may trigger the emergence of new nevus pigmentosus.

Risk factor

Almost everyone has at least one nevus pigmentosus. Approximately 1% of the population is born with one or more congenital nevus pigmentosus, most of which are not hereditary. Meanwhile, individuals with fair skin tend to have more nevus pigmentosus compared to those with darker skin.

Nevus pigmentosus that arises during childhood (ages 2 to 10) is usually the most prominent and persistent throughout life. In contrast, nevus pigmentosus that appears in late childhood or adulthood is typically a result of sun exposure and may fade or shrink over time.

Symptoms

The appearance of nevus pigmentosus can vary. The following are characteristics of nevus pigmentsous:

• Nevus pigmentosus can occur anywhere on the body.
• Nevi may exhibit different appearances on various body parts.
• Nevi can be flat or raised.
• The color of the nevus may vary from pink, flesh tone to dark brown, blue, or black.
• In fair-skinned individuals, nevi tend to be lighter in color, whereas in darker-skinned individuals, they are often dark brown to black.
• Although most nevus pigmentosus are round or oval, their shapes can occasionally be atypical.
• The size of the nevus varies, with diameters ranging from a few millimeters to several centimeters.

Diagnosis

Nevus pigmentosus is typically diagnosed based on its appearance. If there is any doubt in the diagnosis, further examinations, such as dermatoscopy, may be conducted. This examination is especially necessary if:

• The nevus changes in size, shape, structure, or color.
• A new nevus appears in adulthood (>40 years).
• The nevus exhibits characteristics that differ from the typical nevus.
• The nevus demonstrates the ABCDE characteristics (asymmetry, border irregularity, color variation, diameter > 6 mm).
• The nevus bleeds, crusts, or itches.

In such cases, the doctor may also perform a skin biopsy. This examination is the only method to confirm or rule out the presence of skin cancer. The technique employed is excisional biopsy, which is conducted to remove cancerous cells along with surrounding skin tissue to ensure no cancerous cells remain.

Management

Most nevus pigmentosus are harmless and do not require treatment or therapy. However, a nevus may be removed in situations such as:

• A nevus that appears suspicious, resembling skin cancer.
• A nevus that causes discomfort, such as irritation from clothing, combs, or shaving tools.
• If the nevus pigmentosus affects your appearance.

There are several methods to remove nevus pigmentosus, including:

• Shave biopsy: The doctor uses a shaving tool to remove the top layer of skin.
• Punch biopsy: The doctor employs a special punch tool to obtain a skin sample containing both the upper and lower layers of skin.
• Excisional biopsy.
• Electrosurgical destruction.
• Laser treatment to reduce pigmentation or remove coarse hair from the nevus.

Complications

Many individuals express concern about moles due to their association with melanoma, malignant growth of melanocytes and the leading cause of death from skin cancer.

In its early stages, melanoma can resemble a harmless nevus pigmentosus, but over time, its structure becomes irregular and tends to enlarge. Individuals with a greater number of nevus pigmentosus, particularly those with more than 100 nevi, are indeed at higher risk of developing melanoma compared to those with fewer nevi.

However, nevus pigmentosus can also change due to other factors, such as sun exposure or during pregnancy. During these times, a nevus may enlarge, shrink, or even disappear.

Prevention

The number of nevus pigmentosus can be limited by protecting the skin from sun exposure from birth. Sunscreen alone is insufficient to prevent the formation of new nevi.

At any age, sun protection is vital for reducing skin aging and the risk of skin cancer. Methods for skin protection include:

• Covering the skin: Wear hats, long sleeves, and long skirts or pants. Choose fabrics designed to protect the skin from the sun (UPF 40+) when outdoors.
• Apply sunscreen to areas of the body that cannot be covered by clothing. Opt for a broad-spectrum sunscreen with high protection (SPF 50+). Regularly apply sunscreen to exposed areas of the body.

When to see a doctor?

If you are uncertain about any spots or color changes on your skin, it is advisable to consult a doctor. Additionally, if your nevus appears to be changing, such as alterations in color, shape, or size, you should also seek medical advice. This is essential for assessing the possibility of skin malignancy, which can be evaluated through a skin biopsy.

Skin cancer is most easily treated when diagnosed early. Therefore, it is crucial to recognize the signs of skin cancer. Doctors have developed a system known as the ABCDE method to help individuals identify skin cancer warning signs. The ABCDE criteria include:

• A: Asymmetry. Observe whether the nevus has an asymmetric shape.
• B: Border. Nevus pigmentosus should have distinct, clear, and regular borders.
• C: Color. Note if the nevus exhibits uneven color (comprising multiple hues). Also, observe any color changes in the nevus.
• D: Diameter. Be cautious if the size of the nevus exceeds that of a pencil eraser.
• E: Evolving. Look for changes in size, color, shape, or surface of the nevus. Also, note any symptoms such as itching or bleeding from the nevus.

Examine your skin at least once a month. Remember that skin cancer can develop in areas of the body that are not easily visible. Therefore, use a mirror to assist in checking less accessible parts of your body.

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