Quantifying Color Variegation in Melanoma Lesions Using Shannon Entropy

Color variegation is a key dermoscopic sign for melanoma, but lacks objective measurement. We computed Shannon entropy (H) from histograms of smartphone images (iPhone 13 Pro Max) of a histopathologically confirmed superficial spreading melanoma, a benign melanocytic nevus, and their perilesional skin as controls. Relative entropy (ΔH) was calculated to account for baseline skin heterogeneity. Absolute H values were 6.94 (melanoma), 6.67 (nevus), 5.75 (elderly perilesional skin), and 4.39 (young perilesional skin), with ΔH of +1.19 and +2.28, respectively. Entropy differentiated lesions from healthy skin, while ΔH highlighted baseline variability. Limitations include the single-case design, manual region-of-interest delineation, and non-standardized smartphone imaging without controlled lighting or dermoscopic magnification. Shannon entropy provides a reproducible, quantitative measure of color variegation, with potential applications in teledermatology and low-resource settings. Future studies should assess reproducibility across larger cohorts and standardized imaging modalities.