WAIKOLOA, HAWAII (FRONTLINE MEDICAL NEWS) Some melanomas can be diagnosed from the examination room doorway. Others are evident only upon close visual inspection. But the most challenging cases require integration of information regarding the lesion’s dermoscopic pattern in the context of the clues provided by key patient-specific characteristics, according to Dr. Michael A. Marchetti.

“Consider a melanoma diagnosis when a lesion is wrong for the patient’s age, the anatomic location, or skin type, or if it deviates from the patient’s expected signature pattern of nevi,” noted Dr. Marchetti , a dermatologist at Memorial Sloan-Kettering Cancer Center in New York.

A landmark study that provides guidance in this area was conducted several years ago at dermatology centers in four European countries and at Memorial Sloan-Kettering. The investigators enrolled 480 consecutive children and adults with a total of 5,481 melanocytic nevi. The study showcased significant age- and anatomic site–related differences in the distribution of nevi categorized according to dermoscopic subgroups ( Arch Dermatol. 2011;147[6]:663-70 ).

For example, nevi characterized dermoscopically by a peripheral rim of globules were found to be vastly more common during the first 3 decades of life than later. Based upon this study and other data, Dr. Marchetti’s suggested management strategy for peripheral globular nevus with no other concerning features in patients up to age 30 is reassurance that the lesion is not going to be a problem and doesn’t require careful monitoring or biopsy. In a patient beyond age 30, however, frequent monitoring or biopsy is appropriate – and the older the patient with a peripheral globular nevus, the lower the threshold for biopsy.

A peripheral globular nevus is typically a nevus in its radial growth phase, which can continue for years before the nevus enters senescence. The same is true of a nevus that exhibits a Spitzoid starbust pattern on dermoscopy. It is growing radially, and the pretest probability that it’s malignant is highly age dependent.

“In a child, it’s very likely to be a Spitz nevus. In an adult, it’s very likely to be a melanoma. Based upon morphology alone, you really can’t make a distinction between these lesions,” Dr. Marchetti said.

The importance of age in differentiating these starburst lesions was underscored in a recent Italian study involving 384 symmetric, dermoscopically Spitzoid-looking lesions in patients aged 12 or older. Histopathologically, 13.3% of the lesions were diagnosed as melanoma. The probability increased with advancing age, reaching 50% or more after age 50 years. The investigators concluded that the only safe strategy to avoid missing a melanoma is to excise all Spitzoid-looking lesions in patients aged 12 years or older ( J Am Acad Dermatol. 2015;72[1]:47-53 ).

“That concurs with our practice at Memorial Sloan-Kettering. We tend to biopsy all lesions with this particular morphology because you just can’t tell,” Dr. Marchetti said at the Hawaii Dermatology Seminar provided by Global Academy for Medical Education/Skin Disease Education Foundation.

Nevi with a globular dermoscopic pattern occur mostly in children and mainly on the upper back. A globular lesion that develops in an adult or on an extremity is “wrong,” and therefore biopsy should be seriously considered.

In contrast, nevi classified dermoscopically as reticular occur on the trunk and extremities with similar frequency, he continued.

Age and anatomic location are also important considerations in deciding whether a lesion might be a case of nested melanoma of the elderly. This is a form of melanoma first described only a few years ago. It takes the form of a large flat pigmented lesion showing a dermoscopic pattern of irregular globules throughout in a patient over aged 60 years. Notably, three-quarters of cases of nested melanoma of the elderly occur on the extremities ( JAMA Dermatol. 2013;149[8]:941-5 ).

Skin type can raise or diminish the concern that a pigmented lesion is a melanoma. Patients with a lighter skin type tend to have light brown nevi with a patchy reticular network and central hypopigmentation; dark nevi are relatively uncommon in lighter-skinned patients and thus stand out as suspicious outliers. The flip side is also true: Patients with darker skin types tend to have dark nevi with central hyperpigmentation.

A nevus that deviates from a patient’s signature pattern is often referred to as the ugly duckling sign of melanoma.

“It’s the context provided by the background nevi which informs you if there’s an outlier. This can be helpful not only in detecting melanoma, but also in reducing unnecessary biopsies. If a lesion you’re wondering about looks dermoscopically like the patient’s other nevi, that’s reassuring,” Dr. Marchetti said.

He reported having no financial conflicts regarding his presentation. SDEF and this news organization are owned by the same parent company.