Diagnostic Methods: Pattern Analysis, 7-Point Checklist, Comparative Approach

01Pattern analysis is the original method, in which the lesion is examined for global pattern (reticular, globular, cobblestone, homogeneous, starburst, parallel, multicomponent, nonspecific) and for local features (network, dots and globules, streaks, blue-whitish veil, regression, hypopigmentation, blotches, vascular structures). The diagnosis emerges from the overall configuration rather than a numeric score. In the CNMD validation across 108 lesions, pattern analysis produced the highest specificity (83.4%) and the best positive likelihood ratio (5.1), with sensitivity of 83.7%. It remains the preferred method of most expert dermoscopists but requires substantial training to deploy reliably.

02The ABCD rule of dermoscopy assigns weighted points to four parameters: Asymmetry (0-2, weight 1.3), Border abruptness in eight segments (0-8, weight 0.1), Color count out of six possible colors (1-6, weight 0.5), and Dermoscopic structures count (1-5, weight 0.5). The total score interprets as below 4.75 benign, 4.75 to 5.45 suspicious (close follow-up or excision), and above 5.45 highly suspicious for melanoma. Sensitivity in the CNMD was 82.6% but specificity was lower at 70%. The asymmetry parameter alone carried the highest odds ratio (13.7 for two-axis asymmetry).

03The Menzies method requires both negative features (symmetry of pattern across all axes through the lesion centroid AND single color) to be absent for a melanoma diagnosis. If both negative features are present, the lesion is benign. If at least one of the nine positive features (blue-white veil, multiple brown dots, pseudopods, radial streaming, scar-like depigmentation, peripheral black dots/globules, multiple colors, multiple blue-gray dots, broadened network) is present and at least one negative feature is absent, the lesion is diagnosed as melanoma. CNMD sensitivity was 85.7%, specificity 71.1%.

04The seven-point checklist scores three major criteria (atypical network, blue-white veil, atypical vascular pattern) at 2 points each and four minor criteria (irregular streaks, irregular dots/globules, irregular blotches, regression structures) at 1 point each. A total score of 3 or more recommends excision. In the original 1998 study sensitivity was 95% and specificity 75%. Subsequent investigations showed sensitivity ranging from 78% to 100% and specificity from 65% to 87%, depending on the case mix.

05The revised seven-point checklist (Argenziano 2011) addressed a clinical reality: contemporary melanomas are thinner and more inconspicuous than those used to validate the original algorithm. The revision assigns 1 point to every criterion (no major-minor distinction) and lowers the threshold for excision to 1 point. Tested on 100 excised melanomas, 100 excised nevi, and 100 monitored nevi, the revised threshold raised sensitivity from 77.9% to 87.8%, with specificity falling moderately from 85.6% to 74.5%. Atypical network and regression structures emerged as the most sensitive single criteria (each present in about 62% of melanomas).

06The CNMD compared the four lesion-level algorithms head-to-head. All achieved fair to good interobserver agreement and good to excellent intraobserver agreement on the final diagnosis, but pattern analysis was significantly more specific than the simplified methods (P less than .001). Sensitivity differences were smaller. The simplified algorithms were designed for non-experts, accepting reduced specificity to preserve sensitivity. The pragmatic implication is that experienced clinicians should rely on pattern analysis with a low threshold for adding the revised seven-point checklist when uncertainty arises.

07The comparative approach (Argenziano 2011) addresses the patient with multiple atypical nevi, in whom lesion-by-lesion morphologic analysis triggers excessive excisions. Six dermoscopists evaluated 190 lesions from 17 patients with multiple nevi, first individually (morphologic approach) and then grouped by patient (comparative approach). Excision recommendations dropped from 55.1% to 14.1% when lesions were viewed in the context of the same patient's other nevi. Both melanomas in the dataset were correctly identified by all six observers in both rounds. The number-needed-to-excise dropped from 52.3 to 13.4. The comparative approach formalizes the ugly duckling concept and the signature nevus concept: most individuals have a predominant nevus phenotype, and the lesion that does not fit the patient's pattern is the one that warrants attention.

08In contemporary practice the three methods are layered, not chosen exclusively. The clinician applies pattern analysis as the primary engine, falls back to the revised seven-point checklist when the pattern is ambiguous, and overlays the comparative approach across the patient's full nevus pool. Sequential digital dermoscopy imaging and short-term monitoring (covered in the management topic) supplement morphology when the answer cannot be reached at first visit.