Diagnostic accuracy of dermatoscopy for melanocytic and nonmelanocytic pigmented lesions

BackgroundIt is unknown whether dermatoscopy improves the diagnostic accuracy for all types of pigmented skin lesions or only for those that are melanocytic.ObjectiveWe sought to assess if the addition of dermatoscopy to clinical examination with the unaided eye improves diagnostic accuracy for all types of pigmented lesions.MethodsWe analyzed 463 consecutively excised pigmented skin lesions collected during a period of 30 months in a primary care skin cancer practice in Queensland, Australia.ResultsOf 463 lesions, 217 (46.9%) were nonmelanocytic. Overall 30% (n = 138) were malignant including 29 melanomas, 72 basal cell carcinomas, and 37 squamous cell carcinomas. The diagnostic accuracy for malignant neoplasms measured as area under receiver operating characteristic curves was 0.89 with dermatoscopy and 0.83 without it (P < .001). Given a fixed specificity of 80%, the corresponding sensitivity was 82.6% with dermatoscopy and 70.5% without it. The improvement achieved by dermatoscopy was higher for nonmelanocytic lesions than for melanocytic lesions. A short algorithm based on pattern analysis reached a sensitivity of 98.6% for basal cell carcinoma, 86.5% for pigmented squamous cell carcinoma, and 79.3% for melanoma. Among benign conditions, the highest false-positive rate (90.5%) was observed for lichen planus–like keratosis.LimitationsEstimates of diagnostic accuracy are influenced by verification bias.ConclusionsDermatoscopy improves the diagnostic accuracy for nonmelanocytic lesions. A simple algorithm based on pattern analysis is suitable for the detection of melanoma and nonmelanoma skin cancer.