Moles: Types, Warning Signs & When to Worry About Skin Cancer

What Are Moles and Why Do We Get Them?

Moles (melanocytic nevi) are clusters of pigment-producing cells called melanocytes that appear as colored spots on the skin. They develop due to genetics, sun exposure, and hormonal changes. Most adults have 10-40 moles, which typically appear from childhood through age 30-40.

A mole, medically known as a melanocytic nevus, forms when melanocytes—the cells responsible for producing melanin, which gives skin its color—grow in a cluster instead of being spread evenly throughout the skin. This concentration of pigment-producing cells creates a visible spot that is darker than the surrounding skin. The color of a mole depends on how much melanin the cells produce and how deep they are located in the skin.

Moles are incredibly common and are a normal part of human skin development. The average adult has between 10 and 40 moles scattered across their body, though some people may have significantly more or fewer. The number of moles a person develops is influenced by several factors, with genetics playing a primary role. If your parents have many moles, you are more likely to develop numerous moles yourself. Additionally, fair-skinned individuals typically develop more moles than those with darker complexions.

Sun exposure is another major factor in mole development. Ultraviolet (UV) radiation from the sun stimulates melanocyte activity, which can trigger the formation of new moles and darken existing ones. This is why moles often appear more frequently on sun-exposed areas of the body, such as the face, arms, and back. The relationship between sun exposure and mole development underscores the importance of sun protection, particularly during childhood when most mole development occurs.

When Do Moles Appear?

Moles can appear at any age, but their development follows a general pattern throughout life. Some moles are present at birth—these are called congenital nevi and occur in about 1% of newborns. Most moles, however, develop during childhood and adolescence. The formation of new moles typically continues until around age 30-40, after which it becomes less common to develop new moles.

It is entirely normal for the number of moles to increase during childhood and teenage years. During this growth phase, many people notice new moles appearing, sometimes several at a time over short periods. This is generally not a cause for concern. Hormonal changes, particularly during puberty, can accelerate mole development and may also cause existing moles to darken or become more prominent.

Women often notice changes in their moles during pregnancy due to hormonal fluctuations. New moles may appear, and existing moles may darken or enlarge. While these changes are usually normal, any concerning changes should still be evaluated by a healthcare provider. After pregnancy, some of these changes may partially reverse as hormone levels normalize.

Moles on Different Skin Tones

Moles can appear on all skin types and ethnicities, though their appearance may vary. On lighter skin, moles typically appear as tan, brown, or dark brown spots. On darker skin tones, moles may be harder to see or may appear as darker brown or black spots. Regardless of skin color, the same principles for monitoring moles apply—any mole that changes or looks different from your other moles deserves attention.

What Are the Different Types of Moles?

Moles are classified into several types: common moles (junctional, compound, or dermal), atypical (dysplastic) moles, and congenital moles. Common moles are typically round, evenly colored, and smaller than 6mm. Atypical moles have irregular features and carry higher melanoma risk.

Understanding the different types of moles can help you better monitor your skin and recognize when a mole might need medical evaluation. Dermatologists classify moles based on their location within the skin, their appearance, and their risk profile. Each type has distinct characteristics that affect both how they look and their potential health implications.

Common Moles (Acquired Nevi)

Common moles, also called acquired nevi because they develop after birth, are the most frequent type of mole. They are typically small—usually less than 5-6mm in diameter, roughly the size of a pencil eraser. These moles have a uniform color, ranging from tan to dark brown, and feature smooth, well-defined borders. Their shape is usually round or oval, and they may be flat or slightly raised above the skin surface.

Based on their location within the skin layers, common moles are further categorized into three subtypes. Junctional nevi are flat, brown spots located at the junction between the epidermis (outer skin layer) and dermis (inner skin layer). They are typically darker and smoother in appearance. Compound nevi arise from melanocytes in both the epidermis and dermis, making them slightly raised with a central bump. They often have a lighter center with darker edges. Dermal nevi are located entirely within the dermis and are usually flesh-colored to light brown, raised, and dome-shaped. They may also develop hair growth.

Common moles rarely become cancerous. The vast majority remain stable throughout life and pose no health risk. However, having many common moles (more than 50) is associated with an increased risk of melanoma, not because the moles themselves are dangerous, but because a high mole count may indicate greater susceptibility to melanocyte-related conditions.

Atypical Moles (Dysplastic Nevi)

Atypical moles, also known as dysplastic nevi, differ from common moles in several important ways. They tend to be larger than common moles, often exceeding 6mm in diameter. Their shape is frequently irregular or asymmetrical, and their borders may be poorly defined, fading gradually into the surrounding skin rather than having a clear edge. Perhaps most distinctively, atypical moles often contain multiple colors within the same lesion—shades of tan, brown, pink, and sometimes black may all appear in a single mole.

The significance of atypical moles lies in their association with increased melanoma risk. Having one or more atypical moles raises your lifetime risk of developing melanoma. This risk increases further if you have many atypical moles or if melanoma runs in your family. It's important to understand, however, that atypical moles are not cancer and most will never become cancerous. They simply warrant closer monitoring and regular professional skin examinations.

People with dysplastic nevus syndrome (also called familial atypical mole and melanoma syndrome) have numerous atypical moles and a family history of melanoma. These individuals have significantly elevated melanoma risk and benefit from regular dermatological surveillance, often including full-body photography to track changes over time.

Congenital Moles

Congenital moles are present at birth and occur in approximately 1-2% of newborns. They range dramatically in size, from small spots to large lesions covering significant body areas. Small congenital nevi (less than 1.5cm) carry only slightly elevated melanoma risk. Medium-sized congenital nevi (1.5-20cm) have moderately increased risk. Giant congenital nevi (larger than 20cm) carry the highest melanoma risk and require specialized monitoring and often surgical intervention.

The texture and appearance of congenital moles can change over time. They may darken, develop hair, become raised or nodular, or develop an irregular surface. While many of these changes are normal, congenital moles should be monitored regularly by a dermatologist, particularly larger ones. Some giant congenital nevi may be surgically removed due to their melanoma risk and potential cosmetic and psychological impact.

How Do I Know If a Mole Is Dangerous?

Use the ABCDE rule to evaluate moles: A-Asymmetry (uneven halves), B-Border (irregular edges), C-Color (multiple shades), D-Diameter (>6mm), E-Evolution (any changes). Additionally, watch for the "ugly duckling sign"—a mole that looks different from your others.

Recognizing the warning signs of a potentially dangerous mole is one of the most important steps you can take for your skin health. While most moles are completely harmless, melanoma—the most serious form of skin cancer—can sometimes develop within or resemble a mole. Early detection is crucial because melanoma caught in its earliest stages has an excellent prognosis, with 5-year survival rates exceeding 99%. The ABCDE rule, developed by dermatologists, provides an easy-to-remember framework for evaluating moles.

A - Asymmetry

Normal, benign moles are typically symmetrical—if you drew an imaginary line through the center, both halves would look roughly the same. Melanoma, however, often grows unevenly, resulting in asymmetrical shapes. When examining a mole, mentally divide it in half both vertically and horizontally. If either half doesn't match the other in shape, size, or color distribution, this asymmetry warrants attention. Remember that perfect symmetry isn't required for a mole to be normal, but significant differences between the two halves are concerning.

B - Border Irregularity

The edges of a benign mole are usually smooth and well-defined, creating a clear boundary between the mole and surrounding skin. Warning signs include borders that are ragged, notched, scalloped, or blurred. Some concerning moles appear to have projections or irregular extensions into the surrounding skin. A border that fades gradually into the surrounding skin without a clear demarcation can also be suspicious. While some normal moles have slightly irregular borders, dramatic irregularity should prompt medical evaluation.

C - Color Variation

Healthy moles typically have a uniform color throughout—usually a single shade of tan or brown. Melanoma often contains multiple colors within the same lesion. Watch for moles that contain shades of brown, black, red, white, blue, or pink within the same spot. Areas that are significantly darker or lighter than the rest of the mole also merit attention. Complete loss of pigment in part of a previously colored mole (regression) can sometimes indicate melanoma.

D - Diameter

While melanomas can be any size, most are larger than 6mm in diameter—approximately the size of a pencil eraser—when diagnosed. Any mole larger than this threshold deserves careful monitoring. However, it's important to note that melanomas can be smaller, especially in their early stages. Don't dismiss a suspicious mole simply because it's small. This criterion is meant to prompt attention to larger moles, not to provide reassurance about small ones.

E - Evolution

Perhaps the most important warning sign is change. A mole that evolves over time—changing in size, shape, color, elevation, or any other feature—should be evaluated promptly. This includes moles that develop new symptoms such as itching, bleeding, crusting, or tenderness. Even if a changing mole doesn't meet other ABCDE criteria, any evolution in a mole's appearance warrants medical attention. Keeping track of your moles through regular self-examination or photography helps identify changes early.

The Ugly Duckling Sign

In addition to the ABCDE criteria, dermatologists use the "ugly duckling sign" to identify concerning moles. Most of a person's moles tend to look similar to each other—they share common features in terms of size, color, and shape. A mole that looks noticeably different from your other moles—the "ugly duckling"—deserves attention, even if it doesn't meet specific ABCDE criteria. This outlier mole stands out because it doesn't fit the pattern of your other moles.

When Should I See a Doctor About a Mole?

See a doctor if a mole shows ABCDE warning signs, changes in appearance, bleeds or doesn't heal, becomes itchy or painful, or looks different from your other moles. Regular skin checks are recommended for those with many moles, fair skin, or family history of melanoma.

Knowing when to seek medical evaluation for a mole can be the difference between catching a melanoma early—when it's highly treatable—and delayed diagnosis. While the vast majority of moles never require medical attention, certain circumstances should prompt a visit to your healthcare provider or dermatologist. Understanding these scenarios empowers you to take appropriate action without unnecessary worry about normal, benign moles.

The most important reason to see a doctor is any mole that exhibits ABCDE warning signs. If a mole is asymmetrical, has irregular borders, contains multiple colors, is larger than 6mm, or has changed in any way, schedule an appointment with a dermatologist. Even if you're unsure whether a mole is concerning, it's always better to have it evaluated. Dermatologists are trained to distinguish between benign moles and potentially dangerous lesions, often using specialized tools like dermoscopy to examine moles in detail.

Changes in a mole's behavior also warrant medical attention. A mole that begins bleeding without obvious trauma, develops a crust or scab, oozes, or fails to heal should be evaluated promptly. New symptoms such as itching, burning, or tenderness in a previously asymptomatic mole are also concerning. While these symptoms can have benign causes, they can occasionally indicate melanoma or other skin conditions requiring treatment.

Regular Skin Checks for High-Risk Individuals

Some people benefit from regular dermatological surveillance even in the absence of specific concerning moles. High-risk individuals include those with more than 50 common moles or any atypical moles, personal or family history of melanoma, fair skin that burns easily, history of severe or frequent sunburns (especially in childhood), history of tanning bed use, or weakened immune system.

For these individuals, annual full-body skin examinations by a dermatologist are typically recommended. Some may need more frequent monitoring depending on their specific risk factors. During these examinations, the dermatologist will examine all moles and document their appearance, allowing comparison over time. Total body photography and dermoscopic imaging may be used to create a baseline record of all moles.

What to Expect at a Skin Check

A dermatological skin check is a straightforward examination. You'll typically undress to your undergarments, and the dermatologist will systematically examine your entire skin surface, including areas you might not check yourself—like your scalp, between your toes, and your back. A special magnifying device called a dermoscope may be used to examine individual moles more closely.

If the dermatologist identifies a concerning mole, they may recommend a biopsy—removing all or part of the mole for microscopic examination. This procedure is usually quick, performed under local anesthesia, and provides definitive information about whether the mole is benign or malignant. Don't be alarmed if a biopsy is recommended; most biopsied moles turn out to be benign.

How Are Moles Removed?

Moles can be removed through surgical excision (cutting out with margins), shave excision (shaving off at skin level), laser treatment, or diathermy. Suspicious moles must be surgically excised and sent for laboratory analysis. Cosmetic removal uses less invasive methods for confirmed benign moles.

There are several reasons why moles might be removed, and the method used depends largely on the reason for removal. The most important distinction is between moles removed for medical reasons (suspected cancer or to rule out cancer) and those removed for cosmetic or practical reasons (appearance or irritation). This distinction determines both the removal technique and whether the tissue is sent for pathological examination.

When a mole is suspicious for melanoma or other skin cancer, surgical excision is the standard approach. The dermatologist or surgeon removes the entire mole along with a margin of normal-looking skin surrounding it. This margin ensures complete removal if the mole proves to be cancerous and provides tissue for accurate pathological assessment. The excised tissue is always sent to a laboratory where a pathologist examines it under a microscope to determine whether cancer cells are present and, if so, whether the margins are clear.

Surgical Excision

Surgical excision is performed under local anesthesia. The area is numbed, and the mole is cut out using a scalpel along with a small margin of surrounding tissue. The wound is typically closed with sutures (stitches), which are removed after one to two weeks depending on the location. This method leaves a linear scar that usually fades significantly over time but is permanent. Surgical excision is mandatory when there is any concern about malignancy because it allows complete examination of the tissue.

Shave Excision

Shave excision is commonly used for raised benign moles that are being removed for cosmetic reasons or because they catch on clothing or jewelry. After numbing the area, the dermatologist uses a blade to shave the mole off at or just below skin level. This technique doesn't require stitches and heals with a flat or slightly depressed scar. However, because shave excision doesn't remove the deepest portion of the mole, there's a possibility of partial regrowth. This technique is not appropriate for suspicious moles because it doesn't allow for complete pathological examination.

Laser and Diathermy

Laser treatment and diathermy (electrosurgery) can be used to remove certain types of benign moles. Laser treatment uses focused light energy to destroy the mole cells, while diathermy uses electrical current to burn away the tissue. Both methods are quick and typically don't require stitches. However, neither preserves tissue for pathological examination, so they should only be used when the dermatologist is confident the mole is benign. These methods work best for flat, superficial moles and may not be effective for deeper lesions.

What to Expect After Mole Removal

Recovery after mole removal is usually straightforward. The area may be tender for a few days, and you'll need to keep the wound clean and protected. Depending on the method used, you may have stitches that need removal or a wound that heals on its own. Scarring is inevitable with any mole removal, though scars typically fade and become less noticeable over 6-12 months. Sun protection of the healing area is important to minimize scar visibility.

What Other Skin Changes Can Look Like Moles?

Several skin conditions can resemble moles, including seborrheic keratoses (warty growths), solar lentigines (age spots), cherry angiomas (red spots), and skin tags. A dermatologist can distinguish between these benign growths and concerning moles through examination.

Not every brown spot or skin growth is a mole. Several other types of skin lesions can resemble moles but have different origins and implications. Understanding these conditions can help you better describe your skin concerns to healthcare providers and reduce unnecessary worry about benign changes that are a normal part of aging or skin development.

Seborrheic Keratoses

Seborrheic keratoses are extremely common benign growths that often appear in middle age and beyond. They have a distinctive "stuck-on" appearance, as if they were pasted onto the skin surface. Their color ranges from light tan to dark brown or even black, and their surface is often waxy, scaly, or warty. While seborrheic keratoses can resemble moles at first glance, they are completely harmless and never become cancerous. They don't require treatment unless they become irritated or you find them cosmetically bothersome.

Solar Lentigines (Sun Spots/Age Spots)

Solar lentigines, commonly called sun spots, age spots, or liver spots (despite having nothing to do with the liver), are flat, tan to dark brown spots caused by cumulative sun exposure. They typically appear on sun-exposed areas like the face, hands, shoulders, and arms. Unlike moles, which contain clustered melanocytes, lentigines result from increased melanin production in the skin without cellular clustering. While harmless themselves, their presence indicates significant sun exposure, which is a risk factor for skin cancer.

Cherry Angiomas

Cherry angiomas are small, bright red to dark red growths composed of blood vessels. They commonly appear in adulthood and become more numerous with age. Their red color distinguishes them from most moles, though very dark cherry angiomas can sometimes be confused with dark moles. Cherry angiomas are completely benign and don't require treatment. However, any sudden appearance of numerous cherry angiomas should prompt medical evaluation.

Skin Tags

Skin tags (acrochordons) are small, soft, flesh-colored or slightly darker growths that hang off the skin on a thin stalk. They commonly develop in areas where skin rubs against skin or clothing, such as the neck, armpits, and groin. While they can occasionally be mistaken for raised moles, their characteristic pedunculated (hanging) appearance and soft texture distinguish them. Skin tags are harmless but can be removed if they cause irritation or cosmetic concern.

How Can I Protect My Skin and Monitor My Moles?

Protect your skin with daily SPF 30+ sunscreen, protective clothing, and avoiding peak sun hours. Monitor your moles monthly using the ABCDE rule and the ugly duckling sign. Take photos to track changes over time. Get regular professional skin checks if you're at higher risk.

While you cannot prevent all moles from forming—genetics plays a significant role—you can take steps to minimize new mole development and reduce your melanoma risk. Equally important is establishing a routine for monitoring your existing moles so that any concerning changes are detected early. Prevention and early detection work together to protect your skin health.

Sun Protection

The most important step you can take is protecting your skin from ultraviolet (UV) radiation. This means applying broad-spectrum sunscreen with SPF 30 or higher daily, even on cloudy days, and reapplying every two hours when outdoors. Seek shade during peak sun hours (10 AM to 4 PM), and wear protective clothing including wide-brimmed hats, sunglasses, and long sleeves when possible. Remember that UV rays can penetrate clouds and reflect off water, sand, and snow.

Avoid tanning beds entirely. Tanning bed use, especially before age 35, significantly increases melanoma risk. There is no such thing as a "safe" tan from artificial UV sources. If you desire a tanned appearance, consider sunless tanning products, which don't involve UV exposure.

Monthly Self-Examinations

Regular self-examination of your skin allows you to become familiar with your moles and detect changes early. Perform a thorough skin check monthly, examining your entire body including often-overlooked areas like your scalp, between your toes, and your back. Use mirrors or ask a partner to help examine hard-to-see areas. The goal is not just to look at moles but to really know them—their size, shape, color, and location.

Taking photographs of your moles can be extremely helpful for tracking changes over time. You can use your smartphone to document moles and compare images month to month. For larger or more numerous moles, consider asking your dermatologist about total body photography, which creates a detailed baseline record of all your moles.

• Use bright lighting: Examine your skin in a well-lit room
• Be systematic: Check your entire body from head to toe
• Don't forget hidden areas: Scalp, ears, between toes, under nails
• Take photos: Document moles to track changes over time
• Know your moles: Familiarity helps you notice changes