Moles, birthmarks and other types of nevus

There are different types of nevus. Most are just a few millimeters in size, oval or round, flat or slightly raised, and darker than the surrounding skin. But they can also be much larger and a different color or shape. Nevi form on their own or in groups.

Nevi don't cause any physical symptoms. But some might be bothersome, depending on where they are on the body.

Moles, birthmarks and other types of nevus develop if certain cells in the skin grow in clusters. The cells often contain the pigment melanin, or can release melanin into the area around them. These pigmented nevi can often be seen as dark brown spots – particularly on fairer skin.

Even if a nevus like that only appears in childhood or teenage years, its foundations are often laid before birth. Some genetic diseases can lead to especially large numbers of nevi on the body.

Pigmented nevi can also develop over the course of life, especially if your skin is regularly exposed to sunlight without UV protection.

Other types of cells, such as fatty tissue and connective tissue cells, can also form small clusters in the skin and then appear as a spot or wart-like bump.

In “port-wine stains,” the blood vessels in the skin are wider or arranged unusually. The blood that you can see through the skin makes it look reddish. Port-wine stains are there from birth. It is often difficult to tell them apart from hemangiomas (also known as “strawberry birthmarks”). Hemangiomas are benign growths (not cancer) in blood vessels.

Some types of nevus are very common, and others are rarer. That also depends on the color of your skin: People with lighter skin often have small, dark pigmented nevi. Experts believe that every person with light skin has about 20 such nevi on their body. Up to 40 of these marks is also still considered to be normal.

Pigmented nevi are less common in people with darker skin, though. Instead, slate gray nevi (previously known as Mongolian spots) are very common on darker skin and in people of Asian origin. Found in the tailbone area, these nevi are dark, gray-bluish patches of skin that are there from birth but usually disappear over the course of life.

Nevi are either visible from birth or only develop later on. Some fade or disappear over time, while others don't go away.

You can see moles, birthmarks and other nevi just by looking at your skin. If you want to know exactly what type of nevus you have, you can ask your doctor. People who go for skin cancer screening will have their nevi checked there, anyway. In Germany, statutory health insurers cover the costs of this screening every two years from the age of 35.

It is especially important to see a doctor if a nevus

• grows,
• changes shape or color,
• becomes crusty and scabs over,
• itches, or
• bleeds now and then without injury.

Changes like that could be a sign of skin cancer. You should also see a doctor soon if you have a nevus that looks very different to other nevi – perhaps because of an irregular shape, a jagged edge or raised areas – even if it hasn't changed.

The doctor will take a very close look at the spot or area of skin and feel it with their hands. They will sometimes feel the surrounding areas of the body, too. Usually, they will take a close look at all of your skin during the examination. They will sometimes press a see-through glass spatula onto the nevus: If it fades, it has probably developed from blood vessels.

A special kind of magnifying glass called a dermatoscope is used to take a very close look at the surface of the nevi. Some dermatoscopes can also take pictures. That way, the doctor can see whether the nevus has changed during later examinations.

If a nevus is removed because of suspected cancer, the removed tissue is carefully examined under a microscope. Doctors can then see whether it really is cancer and, if so, whether all of the cancer cells have been removed.

Partially or completely raised moles and other nevi might be accidentally scratched open, scraped, or even torn off – especially those that are in a skin fold or somewhere with a lot of contact, like the palm of the hand. Nevi on the scalp might get caught on a comb or hair brush. Those on the face may be cut when shaving. Just like skin elsewhere, injured nevi usually heal by themselves. But the wound can be painful, form a scab, or become infected. Depending on how deep and big the wound is, it might leave a scar behind, making the nevus look different once it has healed.

Moles, birthmarks and other types of nevus are generally harmless. But some types are more likely to turn into melanoma skin cancer, including

• very large congenital (at birth) pigmented nevi with a diameter of 20 centimeters or more,
• dysplastic nevi, where the cells have similarities to cancer cells, and
• if a lot of nevi have formed on your skin over your lifetime – perhaps due to too much sunburn when younger.

It is then best to have your skin checked regularly by a doctor.

Sometimes moles and other nevi can't be seen yet, but their foundations have already been laid from birth and they appear later in life. There is no way to stop that from happening.

But some – known as acquired nevi – can be prevented. They mainly develop if your skin is regularly exposed to the sun without protection. The more acquired nevi you have, the greater the risk of developing melanoma skin cancer. Too much UV light increases the risk of non-melanoma skin cancer, too. So it’s important to protect yourself from UV light – for example, by avoiding the midday sun and tanning beds. When out in the sun, you can use sunscreen, wear a sun hat or cap, and cover your skin with suitable clothing.

Moles, birthmarks and other nevi generally don’t need to be treated. But people who find them bothersome have a number of options: Concealing make-up can be used to temporarily cover them up, and they can be permanently removed with a small surgical procedure. But you should never remove a nevus yourself.

Purely cosmetic treatment isn't covered by health insurers, so you have to pay for it yourself. But they do cover the costs if you have a nevus removed because there's an increased risk that it might turn into cancer.

If you need medical advice about a mole, birthmark or other type of nevus, you can see your family doctor or a skin specialist (dermatologist) about it. Information about health care in Germany can help you to navigate the German health care system and find a suitable doctor. You can use this list of questions to prepare for your appointment.