WAIKOLOA, HAWAII – Sequential dermoscopy imaging (SDI) is a valuable strategy for diagnosing melanomas early and with better sensitivity and specificity, compared with biopsy decisions based solely on the ugly duckling sign, the ABCDs of melanoma, or other aspects of lesion morphology, Michael A. Marchetti, MD, said at the Hawaii Dermatology Seminar provided by the Global Academy for Medical Education/Skin Disease Education Foundation.
Bruce Jancin/MDedge News
Dr. Michael A. Marchetti
SDI entails obtaining repeated dermoscopy images over time in order to detect subtle changes. It is typically done short term, over the course of 3-4 months, or longer term, over a period of 6 months to years, with long-term SDI being reserved for monitoring of less suspicious lesions, often in patients with an atypical mole syndrome.
SDI improves diagnostic specificity by dramatically reducing excision of benign pigmented lesions: in one large Belgian study, by up to 75% (Br J Dermatol. 2012 Oct;167[4]:778-86).
Short-term SDI also improves diagnostic sensitivity. That’s because it enables early identification of clinically featureless melanomas that are detected solely based upon change over a 3-month follow-up period. The operative principle here is that 93%-96% of melanomas will show change on dermoscopy within 3 months, while 99% of unchanged melanocytic lesions are benign. Since 16% of benign nevi will change within 3 months, that means 10%-30% of changed lesions are melanomas.
“If there is any change – it doesn’t matter what the change is, but the two images look different – that should lead to a biopsy,” explained Dr. Marchetti, a dermatologist at Memorial Sloan Kettering Cancer Center, New York.
As a result of this improved sensitivity and specificity, SDI has been shown to reduce the cost per melanoma diagnosis by about 40% (PLoS One. 2014 Oct 14;9[10]:e109339. doi: 10.1371/journal.pone.0109339).
Dr. Marchetti considers SDI a second-level diagnostic test for individual equivocal lesions. His first-level diagnostic tool is total-body photography.
SDI needs to be done by scrupulous examination of digital photographic images side-by-side on a computer monitor. A basic rule of SDI is that it should never be used to monitor raised or palpable lesions.
“The only thing you can monitor is something that’s flat,” he stressed.
Nor should SDI be used to monitor lesions with a peripheral globular pattern. And very slow-growing melanomas could potentially be missed by short-term SDI, so suspected lentigo maligna should be monitored for a minimum of 12 months, according to Dr. Marchetti.
Not every patient with an equivocal melanocytic lesion is a good candidate for SDI. It’s a monitoring strategy that should be reserved for reliable patients who will come back in 3 months. “If a patient doesn’t come back I take that very seriously. We call or send a letter,” Dr. Marchetti said.
Moreover, even in a patient who is a good candidate for SDI, he always offers the option of biopsy today rather than short-term monitoring.
SDI employed in conjunction with total-body photography is an extremely effective means of monitoring patients at very high risk for melanoma, Dr. Marchetti said. The power of this combination was illustrated in a prospective Australian study of 311 patients with a history of invasive melanoma plus either a high-risk genetic mutation or a strong family history. During a median follow-up of 3.5 years, 75 melanomas were detected, 14 of them at the baseline visit. The median thickness of melanomas detected post baseline was in situ. Thirty-nine percent of melanomas were detected using SDI and 38% via total body photography. Roughly one in five biopsied melanocytic lesions proved to be melanoma. Of note, five of the melanomas were more than 1 mm in Breslow thickness: Three of them were histologically desmoplastic, and the other two had nodular components (JAMA Dermatol. 2014 Aug;150(8):819-27).
For dermatologists who need to brush up on their dermoscopy skills, Dr. Marchetti recommended dermoscopedia as a useful, free resource.