What are moles?

A mole is a very common type of skin growth that can occur anywhere on the body. Moles can be flat or raised and sometimes have hair growing from them. Quite often, moles are circular or oval-shaped with smooth edges, but they can also have a rough surface or an irregular shape.

Moles occur when the cells that produce color (pigment) in your skin, known as melanocytes, grow together in clusters. For this reason, moles are also known by the medical name, melanocytic naevi. When moles are brown or black, they are sometimes called pigmented naevi. However, they can also be pink, red, blue, tan or flesh-colored.

Most moles develop on a person before the age of 20, but they can also be present from birth and may fade away later in adult life. They also tend to run in families and are more common in people that have fair skin or spend a lot of time in the sun.

Moles are different to freckles, which tend to appear on light skin as small, brown, flat spots of extra pigment (melanin). Unlike moles though, freckles are not characterized by an increase in the number of melanocytes. Moles are more likely to occur in people with light skin and most Caucasian people will have between 10-40 moles.

Although there are several different types of moles, most are harmless and do not need treatment. However, sometimes a mole can develop into a skin cancer of the melanocytes, called melanoma. Signs of cancer include changes in size, shape or color of the mole. See your doctor if you notice any of these changes.

Causes

Moles occur when melanocyte cells in the skin grow together in clusters. Melanocytes produce the brown skin pigment, known as melanin, which gives skin its normal color. This production of melanin usually occurs in the outer layer of skin, termed the epidermis, and the inner layer, termed the dermis.

On unmarked skin with no growths, the melanin travels to the surface of the skin and spreads evenly to create a uniform color. In a mole, the melanocytes group together in a concentrated spot of melanin. Moles tend to be darker when the clusters of melanocytes are closer to the skin's surface.

It is not known exactly what triggers this clustering of melanocytes in the first place. However, some types of moles run in families, suggesting that certain genes may be passed down from parents to their children. In particular, a gene known as BRAF has been linked to mole development.

Moles are also more likely if you have spent a lot of time in the sun, particularly during childhood. Similarly, moles can appear or change during pregnancy or puberty.

Risk factors

The following factors may increase the likelihood of developing moles:

  • Age  -  the number of moles is usually greatest between childhood and early adulthood;
  • Exposure to sunlight;
  • A family history of moles, and;
  • Hormonal changes, including puberty and pregnancy.

Types

There are a number of different types of mole, including:

Common moles

Also known as acquired moles, these are usually less than a quarter of an inch across and brown, tan or pink in color. Despite also being known as 'acquired growths', it's actually quite uncommon for new moles of this type to develop in adulthood, particularly after the age of 40 years. Instead, the name describes moles that are 'acquired' after birth. The exception is during pregnancy, when the number of common moles can increase quite noticeably.

Common moles can occur anywhere, but most often appear on the upper body, in areas exposed to sunlight. Most common moles do not turn into melanoma. However, you may be at greater risk if you have more than 50 common moles.

Common moles can be further classified as follows:

Junctional moles

Junctional moles are usually flat, circular and brown to black in color. They may also have fuzzy edges. Most moles on the palms, soles and genitals are junctional moles. The name 'junctional mole' comes from where the melanocytes occur, at the junction of the epidermis and the dermis.

Of all the types of common mole, the junctional mole is the most likely to develop into a melanoma.

Compound moles

Compound moles have a raised, dome-shaped area in the center that may be surrounded by a flat edge. This type of mole is usually light brown to black, but in lighter shades than junctional moles. The reason for this is the location of the melanocytes deeper within the inner layer of the skin. However, compound moles may become flesh-colored over time.

Compound moles can grow up to four tenths of an inch across and are often also larger than junction moles. Large compound moles may be hairy, particularly after puberty. Most compound moles are smooth, but some can have a rough surface. These moles very rarely develop into a melanoma.

Intradermal mole

Intradermal moles look like compound moles, but are lighter or skin-colored. This is because the melanocytes are deeper again within the inner layer of the skin. These moles are also thicker and stick out of the skin.

Intradermal moles are sometimes known simply as dermal moles. These moles are benign, meaning they do not develop into melanomas.

Three main types of common moles. 

Atypical moles

Also known as dysplastic moles, these growths look unusual compared to the common moles described above. By unusual, this could mean a mole with one or more of the following characteristics:

  • Large size (greater than one fifth of an inch across);
  • Fuzzy or undefined edges;
  • More than one color, and;
  • Flat and rough surfaces within the same growth.

Atypical moles can occur anywhere on the body, but are most common in areas exposed to the sun, such as the back. The number of atypical moles can vary from just a few to 10 or more. Some people with atypical moles may also have a higher-than-usual number of common moles.

Although atypical moles may look similar to melanoma, it is actually quite unusual for them to turn into cancer. However, people with five or more atypical moles do have an increased risk. If you have a large number of moles or any unusual growths, look out for any changes and visit your doctor to have them checked.

An atypical mole that is characterised by irregular and fuzzy edges.Visual appearance of an atypical mole. 

Congenital moles

Congenital moles are brown or black growths that are present from birth. They are usually oval in shape and grow as the child does. They may also have an irregular shape or change in appearance over time. For example, congenital moles may become bumpy or hairy, fade over time, or become darker at puberty. Congenital moles can also vary in size from less than half an inch across to greater than 7 inches across.

Signs and symptoms

Moles are perhaps most commonly thought of as small, brown spots or growths on the skin. However, there are actually many different types of mole, in a variety of shapes, colors and sizes.

Usually, moles appear in their highest numbers between childhood and early adulthood, then tend to fade after the age of 40. If you develop a mole after the age of 30, there is a greater chance that it could be cancer, so having it checked by your doctor is recommended.

In general though, moles can appear as follows:

  • Shape  -  round, oval or unusual;
  • Color  -  black, brown, tan, pink, red, blue or flesh-colored;
  • Size  -  a tenth of an inch to four inches across, and;
  • Surface  -  flat, raised, rough or smooth.

Methods for diagnosis

To make a diagnosis, your doctor will look closely at any moles and ask questions about your medical history. Photos of each mole next to a ruler may also be taken over time to measure any changes. This photo record is sometimes referred to as a mole map.

If your doctor is concerned about a mole, you may be referred to a dermatologist, who is specialized skin doctor. Sometimes, a mole may need to be removed and examined in a laboratory for signs of cancer. Removing a mole surgically, known as a biopsy, may require a local anesthetic and stitches in the skin.

Local anesthetic

A type of medication that, when administered to an area, creates a localized loss of sensation by blocking nerve activity.

Types of treatment

If your mole is not at risk of developing into a melanoma and it is not causing distress, no immediate treatment is needed. However, if treatment is necessary, one of the following options may be recommended.

Self care

Your doctor will most likely suggest checking moles regularly at home, particularly if they look unusual. As a general guide, moles can be checked using the 'ABCDE' method, which involves looking for:

  • Asymmetry;
  • Border irregularity;
  • Color change;
  • Diameter greater than a quarter of an inch, and;
  • Elevation (raised) and/or evolution (changing shape, color or size).

Skin checks will usually also involve looking at areas of the skin that are not exposed to the sun, such as the scalp, feet, armpits and under the breasts. It may help to use a mirror to look at places that are hard to see.

When a mole is hairy, shaving may be the best option for hair removal, as plucking can cause painful inflammation and swelling. You may also choose to cover visible moles with make-up or concealer products.

Surgery

If your doctor suspects that a mole has developed into melanoma, you will usually be referred to a specialized skin doctor (dermatologist). Once melanoma is confirmed, urgent surgical removal (biopsy) of the mole and surrounding skin is likely.

Surgical removal may also be suggested for cosmetic reasons. For example, depending on the location of a mole, it may cause distress or irritation from clothing or shaving.

Options for surgical removal of a mole include:

Shave biopsy

A shave biopsy is usually recommended to remove raised moles. The procedure is conducted using a local anesthetic and the incision is left to heal gradually. A flat white mark or a small patch the color of the mole may remain after it has healed.

Excision biopsy

An excision biopsy may be conducted for flat moles, or if your doctor suspects melanoma. The procedure is conducted using local anesthetic and the incision is stitched up afterwards. As this involves removal of all layers of affected skin, a thin scar may remain. Moles removed by excision biopsy are usually examined in a laboratory for cancer or other abnormalities.

Local anesthetic

A type of medication that, when administered to an area, creates a localized loss of sensation by blocking nerve activity.

Potential complications

In rare cases, moles can develop into melanoma, a cancer of melanocyte cells in the skin. The following types of mole are more likely than others to become melanoma:

  • Moles that look unusual (atypical moles), particularly if they are larger than 6 mm across or run in your family;
  • Large moles that have been present since birth (congenital moles), and;
  • Moles that are present in high numbers, for example 20-50 or more.

Signs of melanoma include changes in size, shape or color of the mole. A melanoma may become itchy or painful, grow quickly, bleed, ooze or crust over. Visit your doctor if you notice any of these changes.

Prognosis

Moles are so common that they sometimes tend to be considered normal. For this reason, it is possible to live with a number of moles without any problems. However, they can cause embarrassment or irritation if they are large, raised and hairy, or appear in noticeable areas.

It is quite rare for a mole to develop into melanoma, but when it does, the outcome is usually good if diagnosis and treatment occur early. Skin checks at home and with your doctor are recommended after removal to prevent melanoma from coming back.

Prevention

Moles tend to run in families and are more common in people with fair skin, or who spend a lot of time in the sun. For this reason, moles can only be prevented to a degree by:

  • Staying out of the direct sun;
  • Applying sunscreen with a high sun protection factor (SPF15 or above);
  • Covering the skin with a hat, clothing and sunglasses, and;
  • Avoiding tanning beds or artificial sunlamps.

These measures can also help to prevent development of melanoma and other skin cancers.