About Nevus (Moles)

What Is a Nevus?

A nevus, or mole, is an area of benign growth on the skin formed by a cluster of pigmented skin cells. Some moles are present at birth, while others develop later in life. Many moles that develop during adulthood are related to sun exposure and effects on melanin production. Moles can come in a variety of colors, including brown, red, pink, and flesh-colored. Some moles may also have hairs that grow from them. Most moles are benign (noncancerous), but it's still important to keep an eye on them for any changes that could indicate cancer growth. Nevus is the medical term for a mole, and it is very common. Most people have between 10 and 40 moles. There are different types of nevi, some harmless and others more serious. If you notice any changes in the color, size, shape, or height of a mole, or if it starts to itch, bleed, or ooze, it's important to consult with a healthcare provider.

What Causes a Nevus?

The physiologic causes of nevus are not well understood, but it is believed to be a combination of genetic factors and sun damage. Moles are concentrations of pigment-producing cells (melanocytes) in the skin. They tend to appear during childhood and adolescence and can change in size and color over time.

Non-modifiable risk factors for nevus include:

Age: Moles tend to appear more frequently as you get older.
Genetic factors: Family history of moles or melanoma can increase the risk.

Modifiable risk factors for nevus are not well established, but may include:

Sun exposure: Excessive sun exposure, especially during childhood and adolescence, may increase the risk of developing moles.
Hormonal changes: Moles may appear or change during times of hormonal fluctuations, such as pregnancy.

It's important to note that while these factors may be associated with an increased risk of developing moles, they do not guarantee the development of moles or melanoma. Regular skin examinations and sun protection measures are recommended.

Nevus Symptoms

What Does a Nevus Look Like?

A nevus can vary in appearance. Common moles are usually evenly colored brown, tan, pink, or skin-colored spots or bumps. They may be flat or raised, round or oval, and generally smaller than 6 millimeters across, about the width of a pencil eraser.

Even color throughout the mole, commonly brown, tan, pink, or skin-colored.
Round or oval shape with a smooth, well-defined border.
Usually smaller than 6 millimeters across, although some benign moles can be larger.
Flat or raised surface that stays stable over time.
Possible hair growth from the mole, which can occur in benign moles.

When Should a Nevus Be Evaluated?

Moles or other skin spots should be evaluated by a healthcare professional if they are new, changing, or different from other spots on your skin. A helpful way to remember warning signs of melanoma is the ABCDE rule:

Asymmetry: One half of the mole or spot does not match the other half.
Border: The edges are irregular, ragged, notched, blurred, or poorly defined.
Color: The color is not the same throughout and may include different shades of brown, black, tan, pink, red, white, or blue.
Diameter: The spot is larger than 6 millimeters across, about the size of a pencil eraser, although melanoma can sometimes be smaller.
Evolving: The mole or spot is changing in size, shape, color, or height, or develops new symptoms such as itching, tenderness, bleeding, crusting, oozing, or not healing.

Some benign moles can look unusual, and some melanomas may look like ordinary moles. A mole that looks noticeably different from your other moles, sometimes called an “ugly duckling,” should be checked by a healthcare professional.

If you notice a new, changing, bleeding, painful, itchy, or non-healing mole or skin spot, or if you are unsure whether a mole is normal, consult a healthcare professional for evaluation.

How Is a Nevus Diagnosed?

A healthcare professional, often a dermatologist, usually diagnoses a nevus by asking about your medical and family history and examining your skin. They may ask when the mole appeared, whether it has changed, whether it causes symptoms such as itching or bleeding, and whether you have a personal or family history of atypical moles or skin cancer. Many benign moles can be identified by their appearance, but a suspicious or changing mole may need closer evaluation.

History and Physical Exam: The healthcare provider will take a detailed history regarding the appearance of new moles or changes in existing moles, and factors such as family history and sun exposure. They will visually examine the moles for size and characteristics.
Dermoscopy: A healthcare professional may use a handheld device called a dermoscope to look more closely at the mole. Dermoscopy can help assess patterns of color, pigment, blood vessels, and structure that may not be visible to the naked eye. It is painless and noninvasive, but it does not replace a biopsy when a mole appears suspicious.
Biopsy: If a mole looks suspicious or has concerning changes, the healthcare professional may remove all or part of it and send the tissue to a laboratory. A specialist examines the tissue under a microscope to determine whether the mole is benign, atypical, or cancerous.

Additional evaluation depends on what the healthcare professional sees during the skin exam, your risk factors, and whether the mole has changed. Most benign-appearing moles do not need testing, but suspicious moles may need biopsy and pathology review.

Excisional biopsy: In many cases, if a mole is suspicious for melanoma, the entire visible lesion is removed with a small margin of normal-looking skin and sent for pathology testing. If melanoma is diagnosed, additional treatment, such as a wider excision, may be recommended based on the pathology results.
Sentinel lymph node biopsy: This test is not used to diagnose a typical benign nevus. It may be discussed after melanoma has been diagnosed, depending on features such as tumor thickness and other pathology findings. The procedure helps check whether melanoma cells have spread to nearby lymph nodes.

These evaluations are usually performed by a healthcare professional trained in skin examination, such as a dermatologist. They can recommend monitoring, dermoscopy, biopsy, or referral based on the mole’s appearance, your history, and your individual risk factors.

How Is a Nevus Treated?

Should a Nevus Be Removed?

The goals of nevus treatment may include:

Monitor changes: Regularly monitor the size, color, and shape of moles for any potential changes that could indicate skin cancer. This can be done through self-examination or with the help of a dermatologist.
Prevent further development: Limit sun exposure to prevent the development of more moles and reduce the risk of changes in existing moles. This includes wearing protective clothing, using sunscreen, and seeking shade when the sun is strongest.
Removal: Depending on the type and characteristics of the mole, removal may be recommended. The methods of removal include:
- Shave biopsy: A superficial removal of the mole using a scalpel or razor blade.
- Excisional biopsy: Surgical removal of the entire mole, especially for cancerous or suspicious moles.
- Laser treatments: Effective for certain types of moles, laser therapy destroys melanocytes responsible for pigmentation.
- Dermabrasion: A technique that removes superficial lesions on the face using mechanical exfoliation.
- Voltaic arc dermabrasion (VAD): A newer method used for skin resurfacing and removing skin lesions.

Consult a healthcare professional to determine the appropriate approach to monitoring or treating a nevus based on your individual circumstances.