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.