NEW ORLEANS Although the concept of checking the skin for melanoma may be to "find the ugly duckling," the first challenge is to identify the signature nevus in order 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.
She discussed several varieties of signature melanocytic nevi at a dermatology update sponsored by Tulane University. She highlighted a few of the more common types as well as the two most challenging.
Solid brown nevi, she said, are easier to manage. "This type of signature nevus is easy to follow, as it is symmetric and uniform in color," noted Dr. Bolognia, professor of dermatology at Yale University, New Haven, Conn.
Because of their size, the large moles that resemble fried eggs and are often found on the back are frequently of concern to patients and their relatives as well as to non-dermatologists. These "sensational" nevi are benign, and rather than being labeled as precursors of melanoma, they should be viewed as a phenotypic marker, alerting the physician that the patient's entire skin is at risk and should therefore be carefully examined.
"A melanoma can arise in this type of nevus, just as it can any other compound nevus," she said. "Do look for superimposed changes, but in and of themselves, these nevi are benign." Prophylactic excision is not recommended for fried-egg nevi, as scarring can be significant given their size and truncal location. In addition, these nevi age over time with gradual fading of the shoulder component into the surrounding skin and formation of a skin-colored intradermal nevus centrally.
On other hand, the "cheetah" phenotype, represented by numerous small, dark nevi, can be very difficult to manage, she noted. The signature nevus is a dark 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.
"Usually, the patient has 200 or more of these nevi, often admixed with solar lentigines. The anticipation is that this patient will undergo multiple biopsies, with a lower 'hit rate' for cutaneous melanoma than with other types of nevi," she said. "I share these patients with another dermatologist. Having two sets of eyes doing a skin examination is my solution to the difficult 'cheetah' phenotype."
The "eclipse" nevi resemble a solar eclipse, with a solid tan center and a brown rim that is often stellate. The rim may also be discontinuous, leading to asymmetry. They are often seen on the scalp of children, and can be the first sign that a child will be "moley."
"These nevi are benign but they get attention because of their irregular outline and variation in color. Unless there is a superimposed change, they should not elicit concern," she noted. "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."
Dr. Bolognia does not recommend surgically removing eclipse nevi on the scalp because others will probably develop and parents will expect these to be removed as well. Cockarde or "target" nevi are in the same family as eclipse nevi; these types are often seen together.
Another difficult, though rare, phenotype is represented by multiple pink nevi. These patients tend to be skin type 1 or 2 and they produce little, if any, melanin in their nevi. "In this patient the pigment pattern is missing, the road signs are gone, and these nevi can be difficult to evaluate clinically," she said.
"If the nevus has substance (not soft like an aging dermal nevus), I take a second look. And I also look for the nevus with the darkest pink color or any red lesion. I usually biopsy the latter, unless it is clearly acneiform, and like with the 'cheetah' phenotype, share these patients with another dermatologist," she said.
Multiple halo nevi, seen most often in patients in their late teens and early 20s, can also be problematic. There are four stages of halo nevi, with stages I and II being characterized by a depigmented halo surrounding either a pigmented nevus (I) or a pink nevus (II). Stage III appears as an area of depigmentation that is oval or circular in shape (with no central nevus), thus resembling a patch of vitiligo, while stage IV represents complete repigmentation. While everyone with multiple halo nevi deserves a total body examination, if an older adult presents with multiple halo nevi, the possibility of an immune reaction to an ocular (or cutaneous) melanoma needs to be considered, Dr. Bolognia said.