Diagnostic Accuracy of Dermoscopic Features in Acral Lentiginous Melanoma

Importance: Acral lentiginous melanoma (ALM) is a rare but aggressive melanoma subtype. Distinguishing ALM from acral nevi remains difficult, underscoring the need for reliable dermoscopic criteria. Objective: To systematically evaluate dermoscopic patterns that differentiate ALM from benign acral nevi. Data Sources: Embase, PubMed, Web of Science, MEDLINE, and the Cochrane Library were searched from January 1970 through March 2023 using controlled vocabulary (MeSH and Emtree) and natural language terms associated with acral melanoma, nevi, and diagnostic techniques. Searches were limited to English-language and human studies. Data analysis was conducted on November 1, 2024. Data Extraction and Synthesis: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, reviewers independently extracted study data. Pooled proportions and prevalence differences were assessed using random-effects models. Main Outcomes and Measures: The main outcome was the prevalence of dermoscopic features, including parallel ridge, parallel furrow, latticelike, multicomponent, and other pigmentation patterns, with pooled differences between ALM and nevi. Results: Forty-one studies were included, comprising 8845 acral nevi (from 35 studies) and 801 ALMs (from 18 studies). The parallel ridge pattern was the most sensitive and specific feature for ALM (79.6% [95% CI, 71.4%-87.8%] vs 0.6% [95% CI, 0.3%-0.9%] in nevi; pooled difference, -77.3%; 95% CI, -85.0% to -69.6%; P < .001). Multicomponent structures were also significantly associated with ALM (45.8% [95% CI, 19.3%-72.2%] vs 5.0% [95% CI, 3.7%-6.2%] in nevi; pooled difference, -38.5%; 95% CI, -65.7% to -11.2%; P = .01). Conversely, parallel furrow (51.8% [95% CI, 46.7%-56.8%] in nevi vs 8.9% [95% CI, 5.3%-12.5%] in ALM; pooled difference, 41.3%; 95% CI, 33.1%-49.5%; P < .001) and latticelike patterns (13.0% [95% CI, 10.6%-15.5%] in nevi vs 2.7% [95% CI, 1.0%-4.5%] in ALM; pooled difference, 8.9%; 95% CI, 4.2%-13.6%; P < .001) were significantly more common in nevi. Other features, including fibrillar, homogeneous, globular, reticular, other, and nontypical patterns, showed inconsistent or nonsignificant associations. Conclusions and Relevance: While the parallel ridge and parallel furrow patterns remain key diagnostic indicators of ALM and benign acral lesions, this systematic review and meta-analysis establishes the additional diagnostic significance of multicomponent and latticelike features. Nearly 20% of ALM lacked the parallel ridge pattern, demonstrating the need for new specific features for melanoma diagnosis. These findings provide evidence-based benchmarks to potentially improve diagnostic accuracy, guide dermoscopy training, and enhance early detection of ALM.