Evaluating Dermoscopic Features of Nail Unit Squamous Cell Carcinoma: A Systematic Review and Sub-Analysis.

Introduction: The diagnosis of nail unit squamous cell carcinoma (nSCC) remains challenging due to variable clinical presentations and nonspecific features. Dermoscopy offers a promising noninvasive adjunct to improve diagnostic accuracy, but dermoscopic features of nSCC are not well standardized nor summarized. Methods: We systematically reviewed dermoscopic features of keratinocyte-derived nail tumors to identify structures and patterns that differentiate nSCC from other lesions. Databases were searched from inception to March 2025. Studies reporting dermoscopic structures/patterns of benign and malignant keratinocyte-derived nail tumors, and onychomatricoma, were included. A sub-analysis assessed the diagnostic performance of specific features in differentiating nSCC from other keratinocyte-derived nail tumors. Results: From 1,159 articles screened, 83 studies met inclusion criteria, with 10 distinct nail tumors identified. Features such as heterogeneous and brown longitudinal melanonychia, white/yellow scale, structureless areas, glomerular vessels, and ulceration were more frequently reported in nSCC. In a sub-analysis of diagnostic value of specific dermoscopic features, subungual hyperkeratosis was significantly associated with nSCC compared to onychomatricoma. Conclusions: While underscoring ongoing diagnostic challenges of nSCC, this study also provides a framework for future prospective multicenter research aiming to establish reliable, standardized dermoscopic criteria. Such efforts are essential to improve early detection and enhance patient outcomes for those affected by nSCC.