Dysplastic (atypical, or Clark’s) Nevus

Pigmented cells in the skin can form benign moles or skin cancer (malignant melanoma). The former is usually a very straightforward diagnosis, while the latter can be more complicated. Dysplastic moles present the greatest challenge to diagnosis. In their appearance on the skin, as well as their features under the microscope, dysplastic moles are located somewhere in between benign moles and malignant melanoma. Therefore, it is more difficult to diagnose them and arrive at the most appropriate treatment.

The first step in managing a dysplastic nevus is performed by a trained dermatologist, who conducts a skin screening using the naked eye. Moles that are more suspicious than others are isolated and later re-examined with a dermatoscope (a lighted microscope allowing for better visualization). If the moles are deemed suspicious enough, a biopsy (removal of a piece of skin for examination under the microscope) is performed.

Dysplastic nevus is a commonly found mole consisting of pigmented cells. These moles get their name from the fact that they’re irregular; not perfectly round, and have uneven color. The significance of these moles lies in the fact that their appearance resembles that of malignant melanoma.

Current medical thought has not achieved consensus on the proper management of these moles. Most dysplastic nevi are harmless and will not turn into skin cancer over a patient’s lifetime. However, in some, the risk of turning into melanoma is increased, and in others, it is impossible to differentiate their features from those of skin cancer.

The next step is examination by a skin pathologist (dermatopathologist). A dermatopathologist is a doctor trained in evaluating skin specimens under the microscope. A skin pathologist examines the biopsy to determine if it most resembles a benign mole or a malignant melanoma. If the sampled mole resembles a benign nevus, but has certain irregular features, the pathologist notes that in her/his report. If the skin sample resembles a malignant melanoma but does not satisfy all characteristics of malignancy, the pathologist characterizes it as “unconventional”, “highly atypical”, or “unusual”. Usually the moles resembling melanoma should be removed with a margin of normal skin. While it is clear that even severely atypical moles are not melanomas, in many cases they resemble melanomas so closely that the proper distinction cannot be made. Therefore, such lesions are excised.

Because evaluation of dysplastic moles is very complex, the skill of the evaluating dermatologist and dermatopathologist are paramount. This is especially true of patients with tens or hundreds of irregular looking moles. Patients with multiple irregular moles should look for a dermatologist trained in dermoscopy because many studies show that such training increases the accuracy of diagnosis.

Alexander Doctoroff, D.O., F.A.O.C.D.
Assistant Chief of Dermatology, Veterans Administration Medical Center
East Orange, New Jersey
Assistant Clinical Professor of Medicine,
University of Medicine and Dentistry of New Jersey.