Dermoscopic Observations: Key Insights and Patterns

At the start of his session, “Nevogenesis and Melanomagenesis: Insights Gained From Dermoscopy,” presented on the second day of Fall Dermatology Week 2022, Ashfaq Marghoob, MD, shared the existing hypotheses and new hypotheses surrounding dermoscopy insights.

He started by presenting how dermoscopy patterns observed in “normal” skin backgrounds led to the “discovery” of incipient nevus nests. He referenced a population-based cohort study examining dermoscopic patterns of nevi in fifth-grade children. About 40% of subjects showed subtle dermoscopic patterns in “normal” skin surrounding nevi. He noted that these background patterns are harder to see in adults, possibly due to age/UV changes. He then presented globular, reticular, and homogenous backgrounds, and shared that they performed a sample biopsy on the “normal” skin with a globular background, including horizontal sectioning, which showed that there were incipient nests of nevi present.

Another point Dr Marghoob discussed was how dermoscopic observations question the “drop-down” and “move-up” theories of nevus evolution. He presented results from 2 dermoscopic studies that showed there was a dermoscopy-histopathology correlation where reticular pattern nevi had a prominent junctional component, and global pattern nevi had a prominent dermal component. Additionally, he addressed the correlation between nevi and age by noting that globular nevi were mostly present in patients aged 15 years or younger whereas older patients presented with reticular nevi. This offers insights into the developmental stages in the history of common moles starting with junction nevi turning to compound nevi and ending with dermal nevi. Thus, Dr Marghoob concluded that in younger years a globular pattern is most prevalent, with about 90% having BRAF V600E mutation. As age progresses, a reticular pattern is most prevalent, with less than 30% having a BRAF V600E mutation, which continues to be the case even later in life. Therefore, Dr Marghoob stressed how the “drop-down” theory can’t possibly be correct following these findings.

As he continued, one of his final insights addressed how dermoscopic observations showcased multiple nevus involutions, including the death mechanism, which ranges from:

• Halo nevus phenomenon
• Peppering type regression – apoptosis
• Transepidermal elimination

The halo nevus phenomenon is a T-cell mediated involution that makes the nevi smaller while the surrounding “halo” repigments back to normal skin, which can take about 8 years to complete. The next involution, regression, presents a “peppering” dermoscopic finding, possibly due to apoptosis. It commonly looks like a lesion that gradually repigments itself back to normal skin. For transepidermal elimination, Dr Marghoob noted that this is a presumptive theory where nevi fade away as time progresses. Notably, this mechanism shows neither a halo nor any sign of regression.

“This is a theory, but it is a plausible one for how many nevi can disappear just by fading away over the course of time,” he concluded.

Reference
Marghoob AA. Nevogenesis and melanomagenesis: insights gained from dermoscopy. Presented at: Dermatology Week 2022; September 14–17, 2022; Virtual.