Dysplastic Nevus (Atypical Mole)

A mole is a group of melanocytes (pigment-making cells) in the skin. Moles begin to arise in the first few months or years of life, and can increase in number with sun exposure. Most moles are the common variant which pose no risk. These are typically brown, pink, or flesh-colored, and round and regular in shape.

A dysplastic nevus is an atypical mole. While benign, these nevi are usually larger, with atypical features such as darker pigmentation, irregular pigmentation, and ill-defined borders. They occur most often on the trunk, arms and legs, and are less common on the face.

There is some controversy over the potential for a dysplastic nevus to become melanoma. While it is observed to occur, patients with numerous dysplastic nevi usually develop new melanomas from areas of normal-appearing skin, and in a higher percentage of patients than in those without dysplastic nevi. Therefore, it is thought that the presence of many dysplastic nevi is a "marker" for patients who have a higher chance of developing melanoma.

When a dermatologist finds a suspicious or atypical nevus on a skin examination, the diagnosis is confirmed with a skin biopsy. The biopsy specimen is then evaluated by a dermatopathologist under the microscope, and a diagnosis is given. A mole is graded by the atypia (disorder of arrangement and appearance) of the nevus cells. A dysplastic nevus may be called mildly, moderately, or severely dysplastic. 


  • Mildly dysplastic nevus - Common finding which usually requires no further treatment

  • Moderately dysplastic nevus - May require a larger excision or close observation of the area.

  • Severely dysplastic nevus - Often a nevus with severe dysplasia may be difficult to differentiate from melanoma and a surgical re-excision is recommended.

Treatment of a dysplastic nevus is surgical. Standard excision with narrow margins (2 millimeters of normal skin) is advised.

Normal Nevi:

Dysplastic Nevi:

A = Asymmetry

Very Symmetrical

 B = Border

Border is Regular

C = Color
Color is Uniform 

D = Diameter

Usually < 6mm 

 E = Evolving

Stable for Years

A = Asymmetry

Very Asymmetrical

 B = Border

Irregular Border

C = Color

Colors Dark/Mixed 

D = Diameter

Often Large 

E = Evolving

Changing Mole

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