Morphological evolution in melanoma in situ using revised pattern analysis.

Sequential digital dermoscopic imaging (SDDI) compares surface microscopy images of skin lesions over multiple time points. We utilized a retrospective SDDI cohort to investigate the development of dermoscopic features associated with malignancy in melanoma in situ (MIS). A total of 124 in situ melanomas were assessed from 110 Caucasian patients aged ≥18 years, with ≥2 serial images obtained between 1999 and 2017 and followed for a mean 41 months (3-142). As a positive control group, 58 invasive melanomas from 53 patients were also reviewed. Change in MIS size or number of colours correlated to time (both p < .001). The odds of MIS displaying ≥3 clues to malignancy also correlated to time (OR 5.6-52.1) (p < .05). 75% of in situ melanomas matched a dermoscopic subtype on final imaging. While a clinically significant minority of in situ melanomas were unchanged or lost dermoscopic features, lesions predominantly increased in morphological complexity over time. Longer follow-up periods allow dermoscopic features associated with malignancy and histopathological progression to develop.