FDA and EMA-approved noninvasive imaging techniques for basal cell carcinoma subtyping: A systematic review

Background: Basal cell carcinoma (BCC), the most common skin cancer, requires accurate subtyping for optimal treatment. While histopathology is the gold standard, noninvasive imaging offers a biopsy-free alternative, though its accuracy remains unclear. Objective: To assess the diagnostic accuracy of Food and Drug Administration- and European Medicines Agency-approved noninvasive imaging techniques for BCC subtyping. Methods: A systematic review included 19 studies (2650 lesions) from EMBASE, Scopus, PubMed, and Cochrane Library (published up to November 30, 2024). Evaluated modalities included dermoscopy, high-frequency ultrasound (HFUS), dermoscopy-guided HFUS (DG-HFUS), optical coherence tomography (OCT), high-definition OCT (HD-OCT), dynamic OCT (D-OCT), line-field confocal OCT (LC-OCT), and reflectance confocal microscopy. Results: Dermoscopy showed moderate accuracy (81.9% sensitivity, 81.8% specificity for superficial BCC [sBCC]). DG-HFUS outperformed HFUS (82.4% sensitivity, 91.3% specificity). LC-OCT had the highest accuracy, achieving 100% sensitivity for infiltrative BCC. D-OCT distinguished subtypes at 150 μm depth; branching vessels at 300 μm increased nBCC risk (relative risk = 1.53, P = .016). HD-OCT had 100% sensitivity for sBCC but lower accuracy for other subtypes. Reflectance confocal microscopy had 88.9% sensitivity for non-sBCC but only 33.3% for aggressive subtypes. Limitations: Study heterogeneity and inconsistent protocols limit comparability. Conclusion: LC-OCT and HD-OCT offer the highest accuracy, while DG-HFUS outperforms dermoscopy and HFUS, making them strong noninvasive alternatives.