Abstract
Distinguishing keratoacanthoma (KA) from well-differentiated cutaneous squamous cell carcinoma (cSCC) remains challenging due to their similar clinical presentations. This study aims to identify reliable clinical and dermoscopic features for differentiating KA from well-differentiated cSCC. A total of 50 KA cases and 102 well-differentiated cSCC cases were included. Clinical and dermoscopic features were systematically collected and analyzed. A novel dermoscopic descriptor, the bud-like appearance, was proposed to characterize KA. Clinically, KA was associated with exophytic appearance (96.0% vs 28.4%) and shorter disease duration (≤3 months: 50.0% vs 11.0%), while cSCC exhibited longer disease duration (≥12 months: 60.8% vs 16.0%) and higher ulceration rates (16.7% vs 2.0%). Dermoscopically, KA was associated with bud-like appearance (92.1% vs 14.1%), central keratin masses (94.7% vs 40.8%), hairpin vessels (44.7% vs 5.6%). The top 3 features with the highest positive predictive value were hairpin vessels (81.0%), bud-like appearance (77.8%), and disease duration (≤3 months) (67.6%). Combining the bud-like appearance with disease duration (≤6 months) achieved a sensitivity of 79.0%, specificity of 97.2%, positive predictive value of 93.8%, and negative predictive value of 89.6%. Clinical validation of this strategy confirmed an overall accuracy of 76.9% (10/13), with no cSCC misdiagnoses. The diagnostic strategy combining the "bud-like appearance" on dermoscopy with a disease duration of ≤6 months showed promising discriminatory potential for distinguishing KA from well-differentiated cSCC.