Moles are small, usually harmless skin growths made up of clusters of pigment-producing cells called melanocytes. Most adults have between 10 and 40 moles scattered across their body. They can be flat or raised, round or oval, and range in color from pink to dark brown or black depending on your skin tone.
How Moles Form
Melanocytes normally spread evenly throughout your skin, giving it its color. A mole forms when these cells grow in a cluster instead of distributing themselves. The pigment-producing cells that make up moles originate from a structure called the neural crest during embryonic development, traveling to the skin along two different pathways. Once there, they can settle in different layers of the skin, which is why some moles sit flush with the surface while others are raised.
Most moles appear during childhood and adolescence, and new ones can keep showing up into your 30s and 40s. After age 50, developing a brand-new mole is uncommon, which is one reason dermatologists pay close attention to new growths that appear later in life. Children’s and teenagers’ moles grow proportionally as the person grows, but that growth eventually levels off.
What a Normal Mole Looks Like
A typical mole is smaller than about 5 millimeters across, roughly the width of a pencil eraser. It has a single, even color throughout: pink, tan, or brown. People with darker skin or hair tend to have darker moles, while those with lighter complexions tend toward lighter ones. The shape is usually symmetrical and round or oval, with smooth, well-defined edges. Some moles are flat, others dome-shaped, and a few may sprout hairs, which is completely normal.
Types of Moles
Moles fall into a few broad categories based on when they appear and how they look.
Common acquired moles are the ones most people have. They develop after birth, usually during childhood, and are small, evenly colored, and symmetrical. These carry very little risk.
Congenital moles are present at birth. They range from tiny spots to large patches that cover significant areas of skin. Larger congenital moles carry a somewhat higher lifetime risk of developing into melanoma, so they’re typically monitored more closely.
Atypical moles have features that set them apart from common ones: they may be asymmetrical, have irregular or blurry borders, contain more than one color, or exceed 5 millimeters in diameter. Some have a “fried-egg” appearance with a raised center and a flat, darker rim. Having atypical moles doesn’t mean you have cancer, but it does signal a higher baseline risk worth tracking. You may hear the term “dysplastic nevus,” which technically refers to a specific microscopic pattern a pathologist sees under a microscope. Many moles that look atypical to the eye turn out to be perfectly ordinary under the microscope, and vice versa.
What Causes Moles to Change
Sun exposure is the biggest environmental factor that drives new moles and changes to existing ones. Ultraviolet radiation stimulates melanocyte activity, which can lead to new clusters forming or existing ones darkening.
Hormonal shifts also play a role. Pigment cells in your skin have estrogen receptors, so when estrogen levels rise during pregnancy, moles can darken or shift in shape. Puberty triggers similar changes. These hormone-related shifts are usually temporary and harmless, but any mole that changes significantly still deserves a look from a dermatologist, because pregnancy and puberty don’t make someone immune to melanoma.
The ABCDE Rule for Screening
Dermatologists use a five-letter framework to help people evaluate moles at home. It’s not a diagnosis, but it’s a reliable way to decide whether a mole warrants professional evaluation.
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth.
- Color: The mole contains uneven shades of brown, black, tan, or patches of white, red, pink, or blue.
- Diameter: The mole is larger than 6 millimeters (about the size of a pencil eraser), though melanomas can sometimes be smaller.
- Evolving: The mole has visibly changed in size, shape, or color over the past few weeks or months.
A mole that hits one of these criteria isn’t necessarily cancerous, but one that checks multiple boxes, especially “evolving,” should be examined promptly.
How Mole Count Affects Risk
The total number of moles on your body is itself a risk factor for melanoma. People with 11 to 25 moles have about 1.5 times the average risk, and that risk roughly doubles with every additional 25 moles. Someone with 100 or more moles is at substantially elevated risk and benefits from regular full-body skin checks. If you have a high mole count plus a family history of melanoma, that combination warrants even closer monitoring.
How Moles Are Removed
Mole removal is straightforward and done under local anesthesia. There are two main approaches. In a shave excision, a thin blade shaves the mole down to the level of the surrounding skin. It’s quick, leaves a small flat mark, and works well for raised moles that need basic analysis. The downside is that shave removal can’t evaluate the deeper margins of a mole, so it isn’t suitable when a dermatologist suspects something that has grown downward into the skin. Moles removed this way are also somewhat more likely to grow back.
Surgical excision cuts the mole out entirely, including a margin of healthy skin around it. This method is preferred when the mole has atypical features or when the dermatologist wants to ensure all potentially abnormal cells are removed. It requires stitches and leaves a thin linear scar, but provides the most complete tissue sample for a pathologist to examine.
In either case, the removed tissue is sent to a lab for analysis. Most results come back benign. If atypical or cancerous cells are found, your dermatologist will discuss whether additional tissue needs to be removed from the site.