Abstract: 【Abstract】 Objective To evaluate the diagnostic value of dermoscopy and reflectance confocal microscopy （RCM）, alone or in combination, for basal cell carcinoma （BCC）. Methods A diagnostic accuracy study was conducted. Patients with clinically suspected BCC were retrospectively collected from the Department of Dermatology, China-Japan Friendship Hospital between May 2022 and March 2025. All patients underwent sequential dermoscopy, RCM, and histopathological examination. Using histopathological findings as the gold standard, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of dermoscopy and RCM alone or in combination for diagnosing BCC were calculated. The agreement between each diagnostic method and histopathological results was assessed using the Kappa test, and diagnostic confidence scores were compared using the Wilcoxon signed-rank test. Results A total of 139 patients with clinically suspected BCC were included. Histopathological examination confirmed BCC in 79 cases （56.83%） and non-BCC in 60 cases （43.17%）. The 60 patients with non-BCC included 34 with benign non-pigmented tumors （24.46%）, 12 with benign pigmented tumors （8.63%）, 10 with malignant non-pigmented tumors （7.19%）, and 4 with melanomas （2.88%）. Using histopathological findings as the reference standard, the Kappa values for dermoscopy alone, RCM alone, and their combination were 0.704, 0.769, and 0.898, respectively （all P < 0.001）. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of dermoscopy alone for diagnosing BCC were 89.87%, 80.00%, 85.54%, 85.71%, and 85.61%, respectively; for RCM alone, the corresponding values were 84.81%, 93.33%, 94.37%, 82.35%, and 88.49%, respectively; dermoscopy in combination with RCM improved these metrics to 94.94%, 95.00%, 96.15%, 93.44%, and 94.96%, respectively. The diagnostic confidence score （M［Q1, Q3］） was 3 （2, 3） points for both dermoscopy alone and RCM alone, whereas their combination increased the score to 3 （3, 3） points, which was significantly higher than that of either dermoscopy or RCM alone （Z = ?4.99, ?4.61, respectively, both P < 0.001）. Conclusion The combined application of dermoscopy and RCM markedly improves the diagnostic accuracy, confidence, and agreement with histopathological findings for BCC, demonstrating superior diagnostic performance compared with either method alone. This integrated strategy effectively combines the macroscopic morphological assessment by dermoscopy with the cellular-level resolution of RCM, demonstrating definite complementary value and providing a reliable basis for non-invasive and precise diagnosis of BCC in clinical practice.

Key words: Carcinoma, basal cell, Dermoscopy, Reflectance confocal microscopy, Combined diagnosis