Moles are pigmented macules, papules, or nodules composed of clusters of melanocytes or nevus cells. Their main significance (other than cosmetic) is their potential for being or becoming malignant. Lesions with characteristics of concern (changing or highly irregular borders, color changes, pain, bleeding, ulceration, or itching) are biopsied.

Almost everyone has a few moles, which usually appear in childhood or adolescence. There are different types of moles (see Table 1: Benign Skin Tumors: Classification of Moles). During adolescence and pregnancy, more moles often appear, and existing ones may enlarge or darken. Moles typically become more raised and less pigmented over the decades.

Mole

An individual mole is unlikely to become malignant (lifetime risk is about 1 in 3,000 to 10,000), but the single best predictor for risk of development of melanoma is the total number of moles. The presence of > 20 moles indicates a higher than average risk for melanoma; patients should be taught to self-monitor for warning signs and have skin surveillance as part of their primary care.

Table 1
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Classification of Moles Type Clinical Characteristics Histology Comments Compound nevus Light brown to dark brown May be slightly or considerably elevated; 3–6 mm Nests of melanocytes at the epidermodermal junction and within the dermis 2nd stage of the life cycle of melanocytic nevi Halo nevus Any type of melanocytic nevus surrounded by a 2- to 6-mm ring of depigmented skin Same as for other moles but with inflammation and loss of melanocytes in halo skin Usually resolves spontaneously but rarely indicates malignant transformation Intradermal nevus Flesh-colored to brown; may be smooth, hairy, or warty Elevated; 3–6 mm Melanocytes and nevus cells confined almost entirely to the dermis 3rd stage of the life cycle of melanocytic nevi Junctional nevus Light brown to nearly black Usually flat but may be slightly elevated; 1–10 mm Clustering of melanocytes at the epidermodermal junction 1st stage of the life cycle of melanocytic nevi Almost always junctional if located on the palms, soles, or genitals Lentigo Uniformly pigmented, brown to black Flat with sharp margins; 0.5–4 mm Increased number of melanocytes at the epidermodermal junction Darker, sparser, larger, and more scattered than freckles; does not darken or multiply with sun exposure Not truly a mole

Diagnosis

• Biopsy

Because moles are extremely common and melanomas are uncommon, prophylactic removal is not justifiable. However, a mole should be biopsied and examined histologically if it has certain characteristics of concern:

• Changing or highly irregular borders
• Color changes
• Pain
• Bleeding
• Ulceration
• Itching

The biopsy specimen must be deep enough for accurate microscopic diagnosis and should contain the entire lesion if possible, especially if the concern for cancer is strong. However, wide primary excision should not be the initial procedure, even for highly abnormal-appearing lesions, because many such lesions are not melanomas. Incisional biopsy does not increase the likelihood of metastasis if the lesion is malignant, and it avoids extensive surgery for a benign lesion.

Treatment

• Sometimes excision

Moles can be removed by shaving or excision for cosmetic purposes, and all moles removed should be examined histologically. If hair growth is a concern for the patient, a hairy mole should be adequately excised rather than removed by shaving. Otherwise, hair regrowth will occur.

Atypical Moles

(Dysplastic Nevi)

Atypical moles (AM) are melanocytic nevi with irregular and ill-defined borders, variegated colors usually of brown and tan tones, and macular or papular components. Management is by monitoring and biopsy of highly atypical or changed lesions. Patients should reduce sun exposure and conduct regular self-examinations for new moles or changes in existing ones.

AM are nevi with a slightly different clinical and histologic appearance (disordered architecture and atypia of melanocytes). Patients with AM are at increased risk of melanoma; risk increases as the number of AM and as sun exposure increase. Some patients have only one or a few AM; others have many.

The propensity to develop AM may be inherited (autosomal dominant) or sporadic without apparent familial association. Familial atypical mole–melanoma syndrome refers to the presence of multiple AM and melanoma in ≥ 2 1st-degree relatives. These patients are at markedly increased risk (25 times) for melanoma.

Symptoms and Signs

AM are often larger than other nevi (> 6 mm diameter) and primarily round (unlike many melanomas) but with indistinct borders and mild asymmetry. In contrast, melanomas have greater irregularity of color, not just tan and brown, but dark brown, black, red, and blue or whitish areas of depigmentation.

Diagnosis

• Regular physical examinations
• Biopsy

Although clinical findings suggest the diagnosis of AM (see Table 2: Benign Skin Tumors: Characteristics of Atypical vs Typical Moles), biopsy of the worst-appearing lesions should be done to establish the diagnosis and to determine the degree of atypia.

Table 2
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Characteristics of Atypical vs Typical Moles Criteria Typical Moles Atypical Moles Age of onset Childhood or adolescence Continue to appear after adolescence Color Flesh-colored, yellow-brown, or black Tan to dark brown with a pink background; often resembling a fried egg, with a dark or light target commonly with a flatter rim than center Pigment often blurred at the edges or notched Diameter 1–10 mm 5–12 mm Location Anywhere on the body Most common on sun-exposed skin but may occur on covered areas (eg, buttocks, breast, scalp) Number of lesions About 10 One to several dozen

One or more atypical-appearing lesions should be biopsied. Patients with multiple AM and a personal or family history of melanoma should be examined regularly (eg, yearly for family history, more often for personal history, of melanoma).

Treatment

Atypical moles can be removed by excision or shaving.

Prevention

Patients with AM should avoid excessive sun exposure and use sunscreens. Also, they should be taught self-examination to detect changes in existing moles and to recognize features of melanomas. Some experts recommend yearly photographs of the skin surface. Regular follow-up examinations may be combined with baseline and follow-up color photographs of most of the patient's body; this method is most useful in patients with many AM.

If patients have a family history of melanoma (whether developing from AM or de novo) or other skin cancers, 1st-degree relatives should be examined. Patients who are from melanoma-prone families (ie, ≥ 2 1st-degree relatives with cutaneous melanomas) have a high lifetime risk of developing melanomas. The entire skin (including the scalp) of members of an at-risk family should be examined.

Last full review/revision September 2008 by Daniel W. Collison, MD

Content last modified February 2012