NEW ORLEANS — Although the focus of checking for melanoma is usually on finding “the ugly duckling,” the real challenge is to identify the signature nevus to determine the patient's particular phenotype, said Dr. Jean Bolognia.
“Identifying the signature nevus will reduce the number of biopsies you perform,” said Dr. Bolognia, who discussed several varieties of signature melanocytic nevi at a dermatology update sponsored by Tulane University. She highlighted the two most challenging phenotypes—numerous lentiginous nevi, the “cheetah” phenotype, and multiple solid pink nevi—and some of the more common types, such as solid brown, eclipse, and multiple halo nevi.
The cheetah phenotype, represented by numerous small, dark nevi, can be difficult to manage, said Dr. Bolognia, professor of dermatology at Yale University, New Haven, Conn. The signature nevus is a brown-black compound or junctional lentiginous nevus that may or may not have a thin medium brown rim. The center of the lesion is extremely dark and solid, without a visible pigment pattern by dermoscopy.
“The patient can have 200 or more of these nevi. The anticipation is that this patient will undergo multiple biopsies, with a lower 'hit rate' for cutaneous melanoma than with other types of nevi. I share these patients with another dermatologist. Having two sets of eyes doing a skin examination is my solution to [this] phenotype.”
Another difficult, though rare, phenotype is represented by multiple pink nevi. Patients with these tend to be skin type 1 or 2 and produce little, if any, melanin in their nevi.
Dr. Bolognia examines for texture and degree of erythema in these nevi. “I also look for the nevus with the darkest pink color or any red lesion [and] biopsy the latter, unless it is clearly acneiform.” Again, she has another dermatologist also check the patient.
In contrast, solid brown nevi are easier to follow because they are symmetric and uniform in color, she noted. The large moles resembling fried eggs are often found on the back and are a source of concern to patients and nondermatologists. However, they are benign, and rather than labeling them as precursors of melanoma, they should be viewed as a phenotypic marker, alerting the physician the patient is at risk and should be closely examined.
A melanoma can arise in this type of nevus, so one should look for superimposed changes. Prophylactic excision is not recommended because scarring can be significant given their size and truncal location. In addition, these nevi age over time with gradual fading and formation of a skin-colored intradermal nevus centrally.
The eclipse nevi resemble a solar eclipse, with a solid tan center and a brown rim that may be stellate and discontinuous, leading to asymmetry. They are often seen on the scalp of children. “These nevi are benign but get attention because of their irregular outline and variation in color. Unless there is a superimposed change, they should not elicit concern. When the signature nevus is an eclipse nevus, you should focus on the 10 to 15 other nevi that are not in this 'family' and look for the one with the most atypical features,” said Dr. Bolognia. She does not recommend surgically removing eclipse nevi because others will probably develop, but if she does biopsy, she makes sure to send the tissue to a dermatopathologist.
Multiple halo nevi are seen most often in younger patients. There are four stages of halo nevi: stages I and II, characterized by a depigmented halo surrounding either a pigmented nevus (I) or a pink nevus (II); stage III, an oval or circular area of depigmentation (with no central nevus), thus resembling a patch of vitiligo; and stage IV, which represents complete repigmentation. Getting from stage I to IV usually takes years and occurs in almost all patients. Everyone with multiple halo nevi deserves a total body skin examination. In older adults presenting with these nevi, one should also consider the possibility of an immune reaction to an ocular or cutaneous melanoma, Dr. Bolognia said.
In the cheetah phenotype, seen here as a cluster of small, dark nevi, the signature nevus may have a thin, lighter brown rim. Courtesy Dr. Jean Bolognia