THE ABCD RULE OF DERMATOSCOPY - HIGH PROSPECTIVE VALUE IN THE DIAGNOSIS OF DOUBTFUL MELANOCYTIC SKIN-LESIONS

Background: The difficulties in accurately assessing pigmented skin le sions are ever present in practice. The recently described ABCD rule o f dermatoscopy (skin surface microscopy at x10 magnification), based o n the criteria asymmetry (A), border (B), color (C), and differential structure (D), improved diagnostic accuracy when applied retrospective ly to clinical slides. Objective: A study was designed to evaluate the prospective value of the ABCD rule of dermatoscopy in melanocytic les ions. Methods: In 172 melanocytic pigmented skin lesions, the criteria of the ABCD rule of dermatoscopy were analyzed with a semiquantitativ e scoring system before excision. Results: According to the retrospect ively determined threshold, tumors with a score higher than 5.45 (64/6 9 melanomas [92.8%]) were classified as malignant, whereas lesions wit h a lower score were considered as benign (93/103 melanocytic nevi [90 .3%]). Negative predio tive value for melanoma (True-Negative divided by [True-Negative + False-Negative]) was 95.8%, whereas positive predi ctive value (True-Positive divided by [True-Positive + False-Positive] ) was 85.3%. Diagnostic accuracy for melanoma (True-Positive divided b y [True-Positive + False-Positive + False-Negative]) was 80.0%, compar ed with 64.4% by the naked eye. Melanoma showed a mean final dermatosc opy score of 6.79 (SD, +/- 0.92), significantly differing from melanoc ytic nevi (mean score, 4.27 +/- 0.99; p < 0.01, U test). Conclusion: T he ABCD rule can be easily learned and rapidly calculated, and has pro ven to be reliable. It should be routinely applied to all equivocal pi gmented shin lesions to reach a more objective and reproducible diagno sis and to obtain this assessment preoperatively.