CLINICALLY ATYPICAL NEVI

By Gary M. White, MD


Clinically atypical nevus This lesion is irregular in shape with multiple colors, including dark black. (On biopsy, it was benign.)


The clinically atypical nevus is a melanocytic pigmented lesion that has features suggesting melanoma. This usually comes in the form of two or more of the ABCDE criteria. (However, a pigmented lesion may be clinically atypical and warrant biopsy without strictly having two of these criteria. For example, a stable mole that suddenly changes usually warrants a biopsy.) There is controversy and confusion over this and the Clark nevus. In fact, a Clark nevus by definition is clinically atypical, resembling melanoma, but not all clinically atypical lesions are Clark nevi. Many dermatologists choose to ignore the term Clark (dysplastic) nevus and simply consider any pigmented lesion as clinically typical or atypical, with the clinically atypical lesions warranting biopsy. Others will use the term Clark nevus in patients with multiple moles with clinically atypical features and a family history of melanoma (see atypical mole syndrome). Studies are ongoing and the debate continues.

Clinical

A clinically-atypical nevus may have any combination of multiple colors, dark black, large diameter (e.g. > 6 mm), irregular shape and/or irregular border (i.e. the ABCDE criteria.).

How to Biopsy

A deep, saucerized biopsy removing the entire lesion plus a border of 2 mm of clinical normal skin is recommended. This technique adequately removed with clear margins 87% of 78 atypical nevi, preventing the need for reexcision [JAAD 2017;77;1096].

Treatment

Any clinically atypical nevus needs to be completely removed and sent for histologic analysis. If the pathology report describes some amount of atypia, the following have been recommended [JAMA Derm 2015;151;212]:

I would add that nevi with moderate to severe histologic atypia need reexcision with 2-5 mm (clear) margins. The key here is that there is a risk that the nevus was an under-diagnosed melanoma. Thus, the pathologist should always comment on margins in the setting of a nevus with moderate to severe histologic atypia.

A study was done comparing shave re-excision vs standard re-excision of atypical nevi saucerized with positive margins [Dermatol Surg 2015 Jul 30 ahead of print]. In that study, shave re-excision was shown to have a lower clearance rate (76.2%) when compared with surgical excision (87.5%).

Additional Pictures

A funny mole on the sole.
Clinically atypical nevus

A bit too irregular in shape and color.
Clinically atypical nevus

New and dark black.
Clinically atypical nevus

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