How Can You Tell If It's a Mole or Skin Cancer?

Telling moles and melanoma apart is not always easy, even for dermatologists with years of training and experience. With that said, there are telltale signs that can help differentiate a benign (non-cancerous) skin lesion from potentially dangerous skin cancer.

When checking for early signs of melanoma, it's helpful to use the ABCDE rule, the abbreviation of which stands for:

  • Asymmetry: An irregular shape
  • Border: Ragged, notched, or blurred edges
  • Color: Variations in color within the mole
  • Diameter: Diameters over 6 millimeters
  • Evolving: Changes in size, shape, color, or appearance

With that said, there are atypical moles, also called dysplastic nevi. These are often larger, oddly shaped, and have more than one color. Atypical moles can look like melanoma but aren't, which is why it is important to have any irregular moles or changes in moles checked out.

This article explains the differences between moles and melanoma based on the ABCDE rule so that you know when it is time to see a dermatologist.


What Moles Look Like

This is an example of a normal mole. Note that it is almost perfectly round.

normal mole

A mole is a benign melanocytic tumor, meaning a non-cancerous skin lesion that develops from pigment-producing cells called melanocytes.

Also known as nevus (singular) and nevi (plural), moles are not usually present at birth but begin to appear during childhood and the teen years. They can either develop on the top layer of skin (epidermis) or just under the skin (dermis).

What Melanoma Looks Like

Here is an example of melanoma. Melanoma differs in that the lesions are usually asymmetrical (lopsided).

Melanoma skin cancer

Melanoma is a type of skin cancer that also develops from pigment-producing melanocytes. The primary cause of melanoma is overexposure to ultraviolet (UV) radiation from the sun or tanning beds.

Melanoma is the most dangerous type of skin cancer, affecting more than 230,000 people globally and causing over 50,000 deaths each year. In the United States, males are around 1.5 times more likely to get melanoma than females.


What Moles Look Like

Normal moles generally have well-defined borders along with uniform coloration. They can either be raised or flat (as pictured).

normal moles

Despite variations in size or color, the vast majority of moles have smooth borders that are clearly separated from the surrounding skin. The color of the mole will also be even rather than mottled.

What Melanoma Looks Like

Notice how this melanoma tumor has a border that is uneven, ragged, and notched. The color also appears to "bleed" around the edges.

Melanoma skin cancer

An uneven border is one of the tell-tale signs of melanoma. By contrast, moles tend to have smoother, more even borders.

Around 20% to 30% of melanomas develop from existing moles, while 70% to 80% arise on seemingly normal skin.

In either case, melanoma tumors will commonly have jagged, uneven borders that set them apart from other benign skin conditions.


Moles can come in different colors. Some may be pink or flesh-colored, while others may be tan or brown (as pictured). Some can be small and freckle-like, while others may look like a Cindy Crawford-style beauty mark.

normal mole color

Irrespective of the color, the one feature that characterizes moles is that the color is consistent. You won't see two or three different colors in a mole, but you can with melanoma.

Moles can change in color without becoming cancerous. For example, moles on the face will often start out brown and get lighter over time. Moles can also raise or flatten (though they typically remain the same size).

What Melanoma Looks Like

In addition to asymmetry, uneven coloration is a hallmark of melanomas. The same lesion can have a range of colors, from tan, orange, and brown all the way to red, black, and blue.

Close up of malignant melanoma

Another clue that a person has melanoma is the so-called "ugly duckling sign."

By and large, the moles on a person's body will all look the same. However, if you step back and look at them in their entirety, there may be some that stand out as being different, either in terms of color, size, or shape.

These "ugly ducklings" may be an early sign of melanoma.


What Moles Look Like

Some moles may be bigger than others, but most are around 1 to 2 millimeters in diameter. On occasion, a mole may be around 5 millimeters in diameter (1/5 inch), but this is rare.

normal moles sizes

Most moles never cause any problems, but, ironically, a person who has more than 50 has a higher risk of developing melanoma. These moles, called acquired moles, appear on the skin after birth (unlike congenital moles you are born with).

While most people have between 10 and 40 acquired moles on their body, having a multitude of moles warrants an annual check-up to examine parts of the body you cannot readily see, like your back and back of your neck.

What Melanoma Looks Like

Any mole over 6 millimeters (1/4 inch) in diameter should be looked at. Melanomas can be tiny, but most are larger than the size of a pea or pencil eraser.

The one pictured here is significantly larger.

Melanoma Skin Cancer

In addition to the diameter of a lesion, the thickness of a lesion is also a red flag. With melanoma, the thicker the tumor, the poorer the outcome (prognosis).

Melanoma that is less than 1 millimeter thick has a low risk of spreading to other parts of the body. Melanoma thicker than 4 millimeters not only had a high risk of spreading (metastasizing) but also a high risk of returning (recurring) after treatment.


What Moles Look Like

A mole really doesn't change if you have one. While some may get a bit darker as you age, they will usually remain the same color, size, and shape.

This includes dermal nevi (pictured) that match the skin color of the surrounding skin.

dermal nevus


Any changes in the color, size, or shape of a mole should be investigated. This includes changes in texture, such as sudden flaking or scaliness.

What Melanoma Looks Like

Melanoma is characterized by change as cancer cells start to multiply and spread. Any change in the size, shape, color, or appearance of a mole is an immediate red flag that melanoma may be involved.

A spot of melanoma.

This includes changes like:

  • The spread of pigment from the edge of a mole into the surrounding skin
  • Redness or a new swelling beyond the border of the mole
  • Change in sensation, such as itching, tenderness, or pain
  • Change in the surface of a mole, including scaliness, oozing, or bleeding
  • The appearance of a new lump or bump

The challenge, of course, is recognizing the changes. Unless you do a regular self-examination, you may not even notice a mole has changed unless it is bleeding or has caused a skin ulcer. This is especially true if you have lots of moles.

The Skin Cancer Foundation is among the organizations that endorse once-yearly skin exams.

Skin Cancer Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Man


Moles and melanoma can be hard to tell apart, but doctors use a system called the ABCDE rule to help spot lesions that may be cancerous.

The ABCDE rule is based on the fact that melanoma tumors tend to be asymmetrical, have ill-defined borders, be unevenly colored, be larger than 6 millimeters in diameter, and change over time. These early signs can help spot melanoma early when it is still highly treatable.

In addition to doing regular self-exams at home, an annual, full-body checkup with a dermatologist is often recommended.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Mccourt C, Dolan O, Gormley G. Malignant melanoma: a pictorial review. Ulster Med J. 2014;83(2):103-10.

  3. Black S, Macdonald-McMillan B, Mallett X, Rynn C, Jackson G. The incidence and position of melanocytic nevi for the purposes of forensic image comparison. Int J Legal Med. 2014;128(3):535-43. doi:10.1007/s00414-013-0821-z

  4. Centers for Disease Control and Prevention. What Are the Symptoms of Skin Cancer?

  5. Skin Cancer Foundation. Annual Exams: Five Easy Steps to Prepare Yourself.

By Timothy DiChiara, PhD
Timothy J. DiChiara, PhD, is a former research scientist and published writer specializing in oncology.