Comparative and complementary diagnostic value of dermatoscopy and clinical close-up photography in skin cancer diagnosis: A study from the MILK10k dataset

Background While dermatoscopy's added value to clinical imaging is known, the standalone value of dermatoscopy and clinical images remains unclear. Objective To quantify the standalone and complementary value of dermatoscopy and clinical close-up imaging across lesion types and reader expertise. Methods In an online reader study, 283 participants diagnosed 1567 paired images (clinical close-up/dermatoscopic) of skin cancers and mimics. The presentation order was randomized. Diagnostic accuracy, sensitivity, and specificity were compared. The effects of modality, reader expertise, and presentation order were analyzed using a generalized linear mixed model. Results Dermatoscopy alone showed higher sensitivity (85.0% vs 74.2%) but lower specificity (66.8% vs 71.9%) compared with clinical close-up images alone. It improved accuracy for melanoma and basal cell carcinoma, but not for nevi. Adding either modality increased the odds of a correct diagnosis. Dermatoscopy raised the odds by 52% (OR = 1.52; 95% CI: 1.36-1.70; P < .001), while clinical close-ups increased the odds by 40% (OR = 1.40; 95% CI: 1.20-1.61; P < .001). Limitations Image-based evaluation simulated teledermatology rather than face-to-face assessment; potential selection and verification bias cannot be excluded. Conclusion Dermatoscopy alone yields higher sensitivity for malignant lesions but lower specificity for nevi than clinical close-up images. The latter provides complementary diagnostic cues, underscoring the value of integrating both modalities for optimal assessment.