Atypical Mole (Clark Nevus or Dysplastic Nevus) Clinical Presentation

Updated: Feb 28, 2022
  • Author: Manuel Valdebran, MD; Chief Editor: Dirk M Elston, MD  more...
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A detailed personal and family history should be obtained, with special attention regarding moles and melanomas. Other important factors to consider are sun exposure habits and recent changes related to their nevi.

Atypical moles may arise anytime during a patient's lifetime. Atypical moles can change over time, and new lesions may develop. Individuals with familial atypical multiple-mole melanoma (FAMMM) syndrome may have one to several hundred atypical moles, whereas those with nonfamilial (sporadic) atypical moles typically have only 1-10 lesions, although they may also present with several hundred lesions.

An individual with atypical moles who is from a family prone to melanoma has a high lifetime risk of developing a melanoma. Rapid and characteristic changes should prompt consideration for excision/biopsy to rule out melanoma.


Physical Examination

Patients with FAMMM syndrome should have a complete cutaneous examination performed at the first office visit and then at least every 12 months for life.

Atypical moles often have a characteristic appearance, although individual lesions may not show all the findings. Typically, they are large pigmented lesions and frequently measure 5-15 mm in diameter and are asymmetric. Atypical moles are usually larger than common moles (>5mm). Borders are usually irregular, notched, and ill-defined. Macular and papular areas may be present within a single lesion (also described as a "fried egg" or “target” appearance). Color is highly variable and ranges from tan to dark brown to pink. [29]

See the images below.

This mole has a characteristic “fried-egg” appeara This mole has a characteristic “fried-egg” appearance. The eccentric papule is an ordinary nevus. The diagnostic histologic features are found in the macular portion of the mole, particularly at the shoulder (ie, where the papule meets the macule). Courtesy of the National Cancer Institute, via Wikimedia Commons.
Atypical nevus. The delicate, hazy, tan, macular r Atypical nevus. The delicate, hazy, tan, macular rim of this lesion, although not clinically dramatic, represents persistent melanocytic proliferation beyond the lateral limits of the common mole at its center. Courtesy of the National Cancer Institute, via Wikimedia Commons.
Atypical nevus. The central portion of this mole i Atypical nevus. The central portion of this mole is a complex papule. The periphery of the lesion is macular, indistinct, slightly pink. Courtesy of the National Cancer Institute, via Wikimedia Commons.

Atypical nevi may appear anywhere on the body, but they most frequently occur on the back, chest, buttocks, breasts, and scalp. Lesions can be found in sun-exposed and sun-protected areas. Patients with FAMMM syndrome may have more than 100 lesions, which is far greater than the average number of common moles (< 50) in most individuals.

Although the diagnosis of an individual atypical mole may be clinically simple, patients often have many nevi, which may make monitoring complex. An excisional biopsy should be considered in the initial evaluation of atypical mole for histologic confirmation of dysplastic nevi versus melanoma. Shallow scoop saucerizations including at least a 2-mm margin of clinically normal skin surrounding the pigmented lesion can be performed if the lesion is removed entirely and care is taken for adequate depth for accurate staging in melanoma. [49]



Atypical nevi may be inherited (FAMMM syndrome) or appear sporadically. [5] Sun exposure may play a part in the distribution patterns of these nevi, but it is not absolutely necessary because atypical moles also appear on sun-protected skin. Patients with FAMMM syndrome are at an increased risk for the development of melanoma, although the individual risk is variable.

In a single unique case, Tchernev and Patterson attribute Clark nevus formation to treatment with telmisartan/hydrochlorothiazide 80 mg/12.5 mg. The authors maintain that the 67-year-old patient developed a nevus that eventually progressed to nevus-associate cutaneous melanoma and that the melanoma was iatrogenic, due to 3 years of antihypertensive medical therapy. [50]