The National Cancer Institute (NCI) has written this booklet (NIH Publication No. 99-3133) 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 ¹" 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 ² and the other sources of NCI information listed under "National Cancer Institute Information Resources ³" 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 ³" section at the end of this booklet.

Glossary Terms

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.

A type of nevus (mole) that looks different from a common mole. A dysplastic nevus is often larger with borders that are not easy to see. Its color is usually uneven and can range from pink to dark brown. Parts of the mole may be raised above the skin surface. A dysplastic nevus may develop into malignant melanoma (a type of skin cancer).

A form of cancer that begins in melanocytes (cells that make the pigment melanin). It may begin in a mole (skin melanoma), but can also begin in other pigmented tissues, such as in the eye or in the intestines.

A benign (not cancer) growth on the skin that is formed by a cluster of melanocytes (cells that make a substance called melanin, which gives color to skin and eyes). A mole is usually dark and may be raised from the skin. Also called nevus.