Moles. What Are They?

Moles. We all have them. But what exactly are they?

Moles are formed when melanocytes (the skin cells that are responsible for the color of our skin) fail to evenly spread out and instead grow in clusters. These concentrations of melanocytes often form colored patches on our skin that can appear tan, brown, black, red, pink or even blue. These are what we call moles.

Types of Moles

Moles are generally classified based on when they appear, what they look like, and their risk of becoming cancerous.


Some of the moles we have are congenital which means we are born with them. These moles are often referred to as birthmarks and they are caused by our genetics.

Congenital moles vary widely in shape, size, and color. They often gradually change as we age, especially when our hormones are shifting (such as when we go through puberty or become pregnant).

However, congenital moles are more likely to form into melanoma than other moles. Because of this, it is important to closely monitor any changes that occur.

If you have any large congenital moles that become sensitive to the touch or drastically change in color, shape, or size, you should have your dermatologist evaluate them as soon as possible.

 Acquired or Common

Acquired moles (often called common moles) are moles that appear on our skin after birth. These moles form primarily due to exposure to UV radiation from the sun.

Acquired moles typically first appear in our childhood, when we are most sensitive to UV radiation. It is common for them to form on areas of our body that are regularly exposed to the sun. But, they can develop anywhere on the body, even in areas that rarely see the light of day.

It is rare for common moles to become cancerous. However, if you have more than 50 common moles, your risk of developing skin cancer increases.

Common moles that change rapidly or form in adulthood should be examined by your dermatologist.


Atypical moles, as the name suggests, are moles that appear irregular in shape, size or color. They are characterized by uneven borders, pebbled texture, and varied color. They are also often larger than a pencil eraser, 6 millimeters or more.

These moles can form on any part of the body but they are typically found on the torso and very rarely seen on the face.

Like common moles, atypical moles are largely caused by overexposure to UV radiation. They are most commonly found on fair skinned people or those who have high sun exposure.

Atypical moles have the potential to develop into cancer. Your risk of getting skin cancer (particularly melanoma) increases if you have more than four atypical moles.

It is important to speak with your dermatologist about any atypical moles you have and to make sure that any changes that occur in these moles are closely watched.