What 

You

Need 

To 

Know 

About

Moles

and

Dysplastic

Nevi

NATIONAL INSTITUTES OF HEALTH

National Cancer Institute

TM

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This booklet is about certain unusual

moles called dysplastic nevi. It also tells

about melanoma, a type of skin cancer.

If you have questions, call the Cancer

Information Service to learn more about

moles and melanoma. The staff can talk

with you in English or Spanish.

The phone number is

1–800–4–CANCER

(1–800–422–6237). The number for

deaf and hard of hearing callers with

TTY equipment is 1–800–332–8615.

The call is free.

Este folleto es acerca de ciertos

lunares en la piel conocidos como

“dysplastic nevi.” También nos describe

la melanoma, un tipo de cáncer de la

piel. Si tiene preguntas, llame al Servicio

de Información sobre el Cáncer para

conocer más acerca de estos temas. Este

servicio tiene personal que habla

español.

El número a llamar es el 

1–800–4–CANCER (1–800–422–6237).

Personas con dificultades de audición

con equipo TTY pueden llamar al

1–800–332–8615. La llamada es gratis.

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U.S. DEPARTMENT OF HEALTH AND 

HUMAN SERVICES

Public Health Service

National Institutes of Health

Contents

Moles 2

Dysplastic Nevi 2

Melanoma 3

Prevention of Melanoma 5

Early Detection of Melanoma 6

Glossary 10

National Cancer Institute Information Resources 13

Other Booklets 15

Pictures of Ordinary Moles and Dysplastic Nevi 16

Pictures of Melanoma 18

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What You Need To Know AboutTM Moles

and Dysplastic Nevi

he National Cancer Institute (NCI) has written

this booklet to help you learn more about

common moles* and unusual ones called dysplastic

nevi or atypical moles. This booklet shows what moles

look like and explains how they may be related to

melanoma, a type of skin cancer. It describes the signs

of melanoma and explains how you can check your

skin for moles that might be cancerous. It also explains

why and how you can protect your skin. Other NCI

booklets about skin cancer and cancer prevention are

listed in the “Other Booklets” section.

Cancer research has led to real progress against

cancer–better survival and an improved quality of life.

Through research, our knowledge about moles and

cancers of the skin keeps increasing. We are finding

new ways to prevent, detect, and treat cancer. The

Cancer Information Service and other sources of NCI

information listed under “National Cancer Institute

Information Resources” can provide the latest, most

accurate information about moles, dysplastic nevi, and

cancer. Publications mentioned in this booklet and

others are available from the Cancer Information

Service at 1–800–4–CANCER. Many NCI

publications are also available on the Internet at the

Web sites listed in the “National Cancer Institute

Information Resources” section at the end of this

booklet.

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*Words that may be new to readers are printed in italics. Definitions

of these and other terms related to moles and melanoma are listed in

the “Glossary” section. For some words, a “sounds-like” spelling is

also given.

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Moles

oles are growths on the skin. Doctors call moles

nevi (one mole is a nevus). These growths occur

when cells in the skin, called melanocytes, grow in a

cluster with tissue surrounding them. Moles are usually

pink, tan, brown, or flesh-colored. Melanocytes are also

spread evenly throughout the skin and produce the

pigment that gives skin its natural color. When skin is

exposed to the sun, melanocytes produce more

pigment, causing the skin to tan, or darken.

Moles are very common. Most people have between

10 and 40 moles. A person may develop new moles

from time to time, usually until about age 40. Moles

can be flat or raised. They are usually round or oval and

no larger than a pencil eraser. Many moles begin as a

small, flat spot and slowly become larger in diameter

and raised. Over many years, they may flatten again,

become flesh-colored, and go away.

Dysplastic Nevi

bout one out of every ten people has at least one

unusual (or atypical) mole that looks different

from an ordinary mole. The medical term for these

unusual moles is dysplastic nevi. The “Pictures of

Ordinary Moles and Dysplastic Nevi” section shows

the differences between ordinary moles and dysplastic

nevi.

Doctors believe that dysplastic nevi are more likely

than ordinary moles to develop into a type of skin

cancer called melanoma. Because of this, moles should

be checked regularly by a doctor or nurse specialist,

especially if they look unusual; grow larger; or change

in color, outline, or in any other way.

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Melanoma

elanoma is a type of skin cancer–one of the most

serious types because advanced melanomas have

the ability to spread to other parts of the body.*

Melanoma begins when melanocytes (pigment cells)

gradually become more abnormal and divide without

control or order. These cells can invade and destroy the

normal cells around them. The abnormal cells form a

growth of malignant tissue (a cancerous tumor) on the

surface of the skin. Melanoma can begin either in an

existing mole or as a new growth on the skin. The

“Pictures of Melanoma” section shows examples of

melanoma. A doctor or nurse specialist can tell whether

an abnormal-looking mole should be closely watched

or should be removed and checked for melanoma cells.

The purpose of routine skin exams is to identify and

follow abnormal moles.

The removal of the entire mole or a sample of tissue

for examination under a microscope is called a biopsy.

If possible, it is best to remove moles by an excisional

biopsy, rather than a shave biopsy.

If the biopsy results in a diagnosis of melanoma, the

patient and the doctor should work together to make

treatment decisions. In many cases, melanoma can be

cured by minimal surgery if the tumor is discovered

when it is thin (before it has grown downward from the

skin surface) and before the cancer cells have begun to

spread to other places in the body. However, if

melanoma is not found early, the cancer cells can

spread through the bloodstream and lymphatic system

to form tumors in other parts of the body. Melanoma is

M

*Melanoma can also develop in the eye, called intraocular melanoma,

or rarely in other parts of the body where pigment cells are found.

The CIS can provide information about the diagnosis and treatment

of intraocular melanoma.

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much harder to control when it has spread. The spread

of cancer is called metastasis.

Doctors and scientists believe that it is possible to

prevent many melanomas and to detect most others

early, when the disease is more likely to be cured with

minimal surgery. In the past several decades, an

increasing percentage of melanomas have been

diagnosed at very early stages, when they are quite thin

and unlikely to have spread. Learning about prevention

and early detection, while important for everyone, is

especially important for people who have an increased

risk for melanoma. People who are at an increased risk

include those who have dysplastic nevi or a very large

number of ordinary moles.

Risk Factors for Melanoma

• Family history of melanoma

• Dysplastic nevi

• History of melanoma

• Weakened immune system

• Many ordinary moles (more than 50)

• Ultraviolet (UV) radiation

• Severe, blistering sunburns

• Freckles

• Fair skin

The National Cancer Institute booklet What You

Need To Know AboutTM Melanoma has more

information about risk factors for this disease.

It is important to remember that not everyone who

has dysplastic nevi or other risk factors for melanoma

gets the disease. In fact, most do not. Also, about half

the people who develop melanoma do not have

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dysplastic nevi, and they may not have any other

known risk factor for the disease. At this time, no one

can explain why one person gets melanoma while

another does not. Research has shown that sun

exposure, especially excessive exposure that leads to

bad, blistering sunburns, is an important and avoidable

risk factor. Scientists are continuing their studies of risk

factors for melanoma.

Prevention of Melanoma

he number of people in the world who develop

melanoma is increasing each year. In the United

States, the number has more than doubled in the past 

20 years. Experts believe that much of the worldwide

increase in melanoma is related to an increase in the

amount of time people spend in the sun.

Ultraviolet (UV) radiation from the sun and from

sunlamps and tanning booths damages the skin and can

lead to melanoma and other types of skin cancer. (Two

types of ultraviolet radiation–UVA and UVB–are

explained in the “Glossary” section.) Everyone,

especially those who have dysplastic nevi or other risk

factors, should try to reduce the risk of developing

melanoma by protecting the skin from UV radiation.

The intensity of UV radiation from the sun is greatest

in the summer, particularly during midday hours. A

simple rule is to avoid the sun or protect your skin

whenever your shadow is shorter than you are.

People who work or play in the sun should wear

protective clothing, such as a hat and long sleeves.

Also, lotion, cream, or gel that contains sunscreen can

help protect the skin. Many doctors believe sunscreens

may help prevent melanoma, especially those that

reflect, absorb, and/or scatter both types of ultraviolet

radiation. Sunscreens are rated in strength according to

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a sun protection factor (SPF). The higher the SPF, the

more sunburn protection is provided. Sunscreens with

an SPF value of 2 to 11 provide minimal protection

against sunburns. Sunscreens with an SPF of 12 to 29

provide moderate protection. Those with an SPF of 30

or higher provide high protection against sunburn.

Sunglasses that have UV-absorbing lenses should also

be worn. The label should specify that the lenses block

at least 99 percent of UVA and UVB radiation.

Early Detection of Melanoma

ecause melanoma usually begins on the surface of

the skin, it often can be detected at an early stage

with a total skin examination by a trained health care

worker. Checking the skin regularly for any signs of the

disease increases the chance of finding melanoma early.

A monthly skin self-exam is very important for people

who have any of the known risk factors, but doing skin

self-exams routinely is a good idea for everyone. 

Here is how to do a

skin self-exam:

• After a bath or shower,

stand in front of a 

full-length mirror in 

a well-lighted room.

Use a hand-held mirror

to look at hard-to-see

areas.

• Begin with the face

and scalp and work

downward, checking

the head, neck,

shoulders, back, chest,

and so on. Be sure to

check the front, back,

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and sides of the arms and

legs. Also, check the groin,

the palms, the fingernails,

the soles of the feet, the

toenails, and the area

between the toes.

• Be sure to check the 

hard-to-see areas of the

body, such as the scalp and

neck. A friend or relative

may be able to help inspect

these areas. Use a comb or a

blow dryer to help move hair

so you can see the scalp and

neck better.

• Be aware of where your moles are and how they

look. By checking your skin regularly, you will

become familiar with what your moles look like.

Look for any signs of change, particularly a new

black mole or a change in outline, shape, size, color

(especially a new black area), or feel of an existing

mole. Also, note any new, unusual, or “uglylooking” moles. If your doctor has taken photos of

your skin, compare these pictures with the way your

skin looks on self-examination. 

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• Check moles carefully during times of hormone

changes, such as adolescence, pregnancy, and

menopause. As hormone levels change, moles may

change.

• It may be helpful to record the dates of your skin

exams and to write notes about the way your skin

looks. If you find anything unusual, see your doctor

right away. Remember, the earlier a melanoma is

found, the better the chance for a cure. 

In addition to doing routine skin self-exams, people

should have their skin checked regularly by a doctor or

nurse specialist. A doctor can do a skin exam during

visits for regular checkups. People who think they have

dysplastic nevi should point them out to the doctor. It is

also important to tell the doctor about any new,

changing, or “ugly-looking” moles.

Sometimes it is necessary to see a specialist. A

dermatologist (skin doctor) is likely to have the most

training in diseases of the skin. Some plastic surgeons,

general surgeons, oncologists, internists, and family

doctors also have a special interest and training in

moles and melanoma.

Melanoma may run in families, and members of

these families are at high risk for the disease. In some

of these families, certain members also have a large

number (usually over 100) of dysplastic nevi. These

people have an especially high risk of developing

melanoma. When two or more family members develop

melanoma, it is important for all of the patients’ close

relatives (parents, brothers, sisters, and children above

the age of 10) to see a doctor and be examined

carefully for dysplastic nevi or any signs of melanoma.

The doctor can then decide how often each person

needs to be seen. (Doctors may recommend that these

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family members have checkups every 6 months.)

Anyone who has a large number of dysplastic nevi also

should be examined regularly.

A doctor may want to watch a slightly abnormal

mole closely to see whether it changes over time.

Pictures taken at one visit may be compared with the

appearance of the mole at the next visit. Sometimes a

doctor decides that a mole should be removed so that

the tissue can be examined under a microscope. The

removal of a mole, called a biopsy, is usually done in

the doctor’s office using local anesthetic. It generally

takes only a few minutes. The patient may require

stitches, and a small scar will remain after healing. A

pathologist examines the tissue under a microscope to

see whether the melanocytes are normal, dysplastic, or

cancerous.

Because most moles, including most dysplastic nevi,

do not develop into melanoma, removing all of them is

not necessary. A doctor can recommend when and

when not to remove moles. Usually, only moles that

look like melanoma, those that change, or those that are

both new and look abnormal need to be removed.

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Glossary

Anesthetics (an-es-THET-iks): Substances that cause

loss of feeling or awareness. Local anesthetics cause

loss of feeling in a part of the body. General anesthetics

put the person to sleep. 

Biopsy (BY-ahp-see): The removal of cells or tissues

for examination under a microscope. When only a

sample of the tumor is removed, the procedure is called

an incisional biopsy or core biopsy. When the whole

tumor is removed, the procedure is called an excisional

biopsy. When a sample of tissue or fluid is removed

with a needle, the procedure is called a needle biopsy

or fine-needle aspiration.

Cancer: A term for diseases in which abnormal cells

divide without control. Cancer cells can invade nearby

tissues and can spread through the bloodstream and

lymphatic system to other parts of the body.

Dermatologist (der-ma-TAH-lo-jist): A doctor who

specializes in the diagnosis and treatment of skin

problems.

Dysplastic nevi (dis-PLAS-tik NEE-vye): Atypical

moles; moles whose appearance is different from that

of common moles. Dysplastic nevi are generally larger

than ordinary moles and have irregular and indistinct

borders. Often their color is not uniform, and ranges

from pink to dark brown; they usually are flat, but parts

may be raised above the skin surface.

Excisional biopsy (EX-sih-zhon-al BY-ahp-see): The

surgical procedure of removing a tumor by cutting it

out. The biopsy is then examined under a microscope.

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Familial dysplastic nevi (fa-MI-lee-yul dis-PLAS-tik

NEE-vye): A condition that runs in certain families in

which at least two members have dysplastic nevi

(atypical moles) and have a tendency to develop

melanoma.

Lymphatic system (lim-FAT-ik): The tissues and organs

that produce, store, and carry white blood cells that

fight infection and other diseases. This system includes

the bone marrow, spleen, thymus, and lymph nodes and

a network of thin tubes that carry lymph and white

blood cells. These tubes branch, like blood vessels, into

all the tissues of the body.

Malignant (ma-LIG-nant): Cancerous; a growth with a

tendency to invade and destroy nearby tissue and

spread to other parts of the body.

Melanocytes (mel-AN-o-sites): Cells in the skin that

produce and contain the pigment called melanin. 

Melanoma: A form of skin cancer that arises in

melanocytes, the cells that produce pigment. Melanoma

usually begins in a mole.

Metastasis (meh-TAS-ta-sis): The spread of cancer

from one part of the body to another. Cells in the

metastatic (secondary) tumor are the same type as those

in the original (primary) tumor. 

Mole: A benign growth on the skin (usually tan, brown,

or flesh-colored) that contains a cluster of melanocytes

and surrounding supportive tissue.

Nevus (NEE-vus): A benign growth on the skin, such as

a mole. A mole is a cluster of melanocytes and

surrounding supportive tissue that usually appears as a

tan, brown, or flesh-colored spot on the skin. The plural

of nevus is nevi (NEE-vye).

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Oncologist (on-KOL-o-jist): A doctor who specializes

in treating cancer.

Pathologist (pa-THOL-o-jist): A doctor who identifies

diseases by studying cells and tissues under a

microscope.

Pigment: A substance that gives color to tissue.

Pigments are responsible for the color of skin, eyes, 

and hair.

Risk factor: Anything that increases the chance of

developing a disease.

Shave biopsy (BY-ahp-see): A procedure in which the

parts of a mole that are above and just below the

surface of the skin are removed with a small blade.

There is no need for stitches with this procedure.

SPF: Sun protection factor. A scale for rating the level

of sunburn protection in sunscreen products. The higher

the SPF, the more sunburn protection it provides.

Sunscreen: A substance that helps to protect the skin

from the sun’s harmful rays. Sunscreens reflect, absorb,

and/or scatter both UVA and UVB radiation. Using

lotions, creams, or gels that contain sunscreens can help

protect the skin from premature skin aging and damage

that may lead to skin cancer. 

Tumor (TOO-mer): An abnormal mass of tissue that

results from excessive cell division. Tumors perform no

useful body function. They may either be benign (not

cancerous) or malignant (cancerous).

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Ultraviolet radiation (ul-tra-VYE-o-let

ray-dee-AY-shun): Invisible rays that are part of the

energy that comes from the sun. UV radiation can

damage the skin and cause melanoma and other types

of skin cancer. UV radiation that reaches the earth’s

surface is made up of two types of rays, called UVA

and UVB rays. UVB rays are more likely than UVA

rays to cause sunburn, but UVA rays pass deeper into

the skin. Scientists have long thought that UVB

radiation can cause melanoma and other types of skin

cancer. They now think that UVA radiation also may

add to skin damage that can lead to skin cancer and

cause premature skin aging. For this reason, skin

specialists recommend that people use sunscreens that

reflect, absorb, and/or scatter both kinds of UV

radiation.

National Cancer Institute Information

Resources

ou may want more information for yourself, your

family, and your doctor. The following National

Cancer Institute (NCI) services are available to help

you.

Telephone

Cancer Information Service (CIS)

Provides accurate, up-to-date information on cancer

to patients and their families, health professionals, and

the general public. Information specialists translate the

latest scientific information into understandable

language and respond in English, Spanish, or on TTY

equipment.

Toll-free: 1–800–4–CANCER (1–800–422–6237)

TTY (for deaf and hard of hearing callers):

1–800–332–8615

Y

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Internet

These Web sites may be useful:

http://www.nci.nih.gov

NCI’s primary Web site; contains information about

the Institute and its programs. 

http://cancertrials.nci.nih.gov

cancerTrialsTM; NCI’s comprehensive clinical trials

information center for patients, health professionals,

and the public. Includes information on understanding

trials, deciding whether to participate in trials, finding

specific trials, plus research news and other resources.

http://cancernet.nci.nih.gov

CancerNetTM; contains material for health

professionals, patients, and the public, including

information from PDQ® about cancer treatment,

screening, prevention, supportive care, and clinical

trials; and CANCERLIT®, a bibliographic database.

E-mail

CancerMail

Includes NCI information about cancer treatment,

screening, prevention, and supportive care. To 

obtain a contents list, send e-mail to

cancermail@icicc.nci.nih.gov with the word “help” in

the body of the message.

Fax

CancerFax®

Includes NCI information about cancer treatment,

screening, prevention, and supportive care. To obtain a

contents list, dial 301–402–5874 from a fax machine

hand set and follow the recorded instructions.

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Other Booklets

he National Cancer Institute booklets listed below

and others are available from the Cancer

Information Service by calling 1–800–4–CANCER.

• What You Need To Know AboutTM Cancer

• What You Need To Know AboutTM Melanoma

• What You Need To Know AboutTM Skin Cancer

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Pictures of Ordinary Moles and Dysplastic Nevi

Ordinary Moles

Evenly tan or brown; all typical

moles on one person tend to look

similar.

Round or oval, with a distinct

edge that separates the mole from

the rest of the skin.

Begin as flat, smooth spots on

skin (1a); may become raised (1b)

and form a smooth bump (1c).

Usually less than 5 millimeters

(about 1/4 inch) across (size of a

pencil eraser).

Between 10 and 40 typical moles

may be present on an adult’s

body.

Usually found above the waist on

sun-exposed surfaces of the body.

Scalp, breasts, and buttocks rarely

have normal moles.

Location Number Size Surface Shape Color Feature

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Dysplastic Nevi

Mixture of tan, brown, and

red/pink. A person’s moles often

look quite different from one

another.

Have irregular, sometimes

notched edges. May fade into

the skin around it. The flat

portion of the mole may be level

with the skin.

May have a smooth, slightly

scaly, or rough, irregular,

“pebbly” appearance.

Often larger than 5 millimeters

(about 1/4 inch) across and 

sometimes larger than 

10 millimeters (about 1/2 inch).

May be present in large numbers

(more than 100 on the same

person). However, some people

have only a few dysplastic nevi.

May occur anywhere on the

body but most frequently on the

back and areas exposed to the

sun. May also appear below the

waist and on the scalp, breasts,

and buttocks.

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Pictures of Melanoma

Large size Most melanomas are at least 5 millimeters

(about 1/4 inch) across when they are found;

many are much larger. An unusually large

mole may be melanoma.

Many colors A mixture of tan, brown, white, pink, red, gray,

blue, and especially black in a mole suggests

melanoma.

Irregular border If a mole has an edge that is irregular or

notched, it may be melanoma.

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Abnormal surface If a mole is scaly, flaky, oozing, or bleeding, has

an open sore that does not heal, or has a hard

lump in it, it may be melanoma.

Unusual sensation If a mole itches or is painful or tender,

melanoma may be present.

Abnormal skin If color from the mole spreads into the 

around mole skin around it or if this skin becomes red 

or loses its color (becomes white or gray), 

melanoma may be present.

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The National Cancer Act, passed by Congress in

1971, made research a national priority. Since that time,

the National Cancer Institute (NCI), the lead Federal

agency for cancer research, has collaborated with top

researchers and facilities across the country to conduct

innovative research leading to progress in cancer

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Permissions Department, National Cancer Institute,

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NIH Publication No. 99–3133

Revised June 1999

Printed September 1999 P028

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