Dermoscopic Insights Into Nevogenesis and Melanomagenesis

Ashfaq Marghoob, MD, presented the session, “Nevogenesis and Melanomagenesis: Insights Gained From Dermoscopy” on the second day of Dermatology Week 2022.

He started off with a discussion of nevogenesis and the concept of incipient nests. “We observed that there were dermoscopic patterns in background ‘normal’ skin,” Dr Marghoob said, “These normal patterns in background skin led to the discovery of some incipient nevus nests.” Globular, reticular, and homogenous backgrounds were seen. “When we did a sample biopsy of the normal skin that had the globular background and then did horizontal sectioning, what we found was that there were indeed incipient nests of nevi present,” he explained. He continued, “We hypothesized that incipient nests may be potential seeds from which at least some ‘acquired’ nevi arise.”

Dr Marghoob noted that these dermoscopic observations bring into question the ‘drop down’ and ‘move up’ theories of nevus evolution. A reticular pattern nevus has a prominent junctional component, whereas a globular pattern nevus has a prominent dermal component, based on results from 2 dermoscopic studies. In a cross-sectional study looking at types of nevi by age, he stated, “In the young cohorts under the age of 15, most of the nevi were globular… In the oldest cohort, most of the nevi were reticular, with very few globular.”

Dermoscopic observations also support that there are “biologically distinct subsets of nevi,” Dr Marghoob said, “Basically, whatever you have initially, that nevus remains the same type of nevus over the course of time.” He also shared information about the growth rate of nevi with a peripheral globular pattern, “From inception to senescence, when the lesion does not change anymore, that magnitude of time is about 49 months.” He suggested that the rate of growth cannot be used to differentiate a nevus from a melanoma and indicated that “dermoscopic observations [have] led to an appreciation that there are multiple mechanisms to nevus involution.”

Dr Marghoob then moved on to melanomagenesis. He offered the insight that “dermoscopic observations support the concept of different stem cell populations giving rise to lentigo maligna melanoma, superficial spreading melanoma, nodular melanoma, and acral lentiginous melanoma.” Dermoscopic observations have also “led to an appreciation for the existence of ‘indolent’ [or] very slow growing melanomas.”

“Another insight gained from dermoscopy is that shiny white lines in melanoma correspond with stromal alteration,” he said, “What we have also noticed is that atypical vessels in the form of dotted and serpentine vessels are also more frequently seen when the shiny white structures are present.” When shiny white lines are present, 88% of the lesions will have vessels present. This is a feature of progression to an invasive melanoma. Dr Marghoob stated that “regression seen on histopathology can be true regression or may, in fact, represent progression.”

Dr Marghoob concluded his session with an inspiring quote from the 1937 Nobel Prize Laureate, “Discovery consists of seeing what everyone else has seen and thinking what no one else has thought.”

Reference

Marghoob AA. Nevogenesis and melanomagenesis: insights gained from dermoscopy. Presented at: Dermatology Week 2022; May 11–14, 2022; Virtual.