Moles (nevi)

Also known as:Nevi pigmentosa

Anatomy or system affected:Skin

Definition: Nonmalignant marks, pigmented spots, or growths on the skin.

Causes and Symptoms

The common mole, also known as a nevus pigmentosus, is a mark, spot, or growth found on the skin that is generally benign and may be either congenital (present at birth) or developmental. Moles may be various colors, shapes, and sizes, and they can be flat or raised. Caucasian adults usually have approximately twenty pigmented nevi, the majority of which are less than 0.5 inch in diameter, with fewer pigmented ones evident at birth.

A mole is primarily the result of an accumulation of melanocytes, cells that form the skin pigment melanin. The greater the number of melanocytes, the darker the brown color of the mole. When the melanocytes are located deep below the skin surface, the mole appears dark bluish in color. Melanocytes also form the relatively larger vascular nevi (birthmarks) that derive from abnormal vascular construction in the skin. Types of birthmarks include the strawberry hemangioma and the port-wine stain, which arise from poorly developed blood vessels, and the nevus anemicus, which is attributed to a reduced blood flow.

Treatment and Therapy

In most cases, moles are benign, but occasionally they develop into malignant melanoma, a form of skin cancer. This transformation may be indicated by the development of a flat, pigmented zone around the base of a mole or the progressive enlargement of an existing mole. Other evidence of skin cancer involves a sudden increase in size, color, texture, shape, or sensation; irregular edges; loss of the hair surrounding a mole; and ulceration and bleeding. These signs that should be monitored are often remembered as ABCDEs: Asymmetry, Border, Color, Diameter, Elevation/Evolution. If cancer is suspected, a doctor can test for cancer cells by performing a biopsy to remove all or part of the mole.

A newly formed mole is usually flat. If it arises between the dermis and the epidermis, then the mole is called a junction nevus, which may become malignant. A dermatologist’s care in a timely manner is usually recommended. The main treatment involves removal of the mole by cauterization or laser treatment.

Moles occasionally disappear with age. Generally, however, more nevi form with aging, and they are usually permanent. The growth of new moles and darkening or other changes in existing ones should be monitored. Moles that are unsightly or irritated may be surgically removed. New moles are usually dome-shaped and elevated slightly above the surrounding skin. Plucking the hair associated with moles is not recommended, as this may damage the skin and lead to ulceration and bleeding.

Similar Conditions

Moles are common, but there are also other conditions that look similar and can easily be confused. Freckles (ephilides) are small brown spots mainly found on the arms or face, especially in the summer; like normal moles they are not a health risk, though they may indicate excessive sun exposure. A skin tag (acrochordon) is a small stalk or flap of skin that hangs apart from the skin surface. They are more common in women and generally are seen in the armpits, neck, chest, and back. They are benign and often form with age. Lentigines, also called liver spots, also often form with age as well as sun exposure, especially in Caucasians. Though benign, they can evolve into melanoma and so should be monitored for changes.

Cherry angiomas (hemangiomas), also called red moles due to their appearance, are not in fact moles. They are small areas of blood vessels raised near the surface of the skin, most commonly seen on the arms, back, or chest. Cherry angiomas are common, especially among adults in their thirties and older, and are not cancerous. Seborrheic keratoses are another noncancerous skin growth, usually appearing as a wartlike brown or black growth on the chest, back, or head. They are formed by keratinocyte cells. Actinic keratoses can also look like moles, typically as a red or red-brown patch of irregular size and shape and with a rough or scaly surface. However, these are not moles, but precancerous spots caused by damage from sunlight. They should be examined by a doctor.

Bibliography

Burns, Tony, et al., eds. Rook’s Textbook of Dermatology. 9th ed. John Wiley & Sons, 2016.

Johnston, Ronald B., and David Weedon. Weedon's Skin Pathology Essentials. 3rd ed. Elsevier, 2023.

Lacouture, Mario E. Dermatology and the Cancer Patient: Conditions of the Skin, Hair, and Nails During Cancer Treatment and Survivors. Wiley, 2013.

McClay, Edward F., and Jodie Smith. One Hundred Questions and Answers About Melanoma and Other Skin Cancers. Jones & Bartlett Learning, 2013.

Mackie, Rona M. Clinical Dermatology. 5th ed. Oxford UP, 2003.

Marks, James G., Jr., and Jeffrey J. Miller. Lookingbill and Marks’ Principles of Dermatology. 6th ed. Saunders, 2019.

"Moles." Cleveland Clinic, 2 Feb. 2021, my.clevelandclinic.org/health/diseases/4410-moles. Accessed 20 July 2023.

Schofield, Jill R., and William A. Robinson. What You Really Need to Know about Moles and Melanoma. Johns Hopkins UP, 2000.

Shenenberger, D. W. "Cutaneous Malignant Melanoma: A Primary Care Perspective." American Family Physician, vol. 85, no. 2, 2012, pp. 161–168.

Turkington, Carol, and Jeffrey S. Dover. The Encyclopedia of Skin and Skin Disorders. 3rd ed. Facts On File, 2007.

Woodhouse, Justin G., and Kenneth J. Tomecki. "Common Benign Growths." Cleveland Clinic Center for Continuing Education, June 2017, www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/dermatology/common-benign-growths. Accessed 26 July 2023.