Minimizing the dermatoscopic morphologic overlap between basal and squamous cell carcinoma: a retrospective analysis of initially misclassified tumours

Background Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) have well‐established dermatoscopic criteria that make them relatively easy to recognize on a clinical basis. However, even with the addition of dermatoscopy, a morphologic overlap between the two tumours does exist. Objectives To analyse the dermatoscopic morphology of clinically and dermatoscopically misclassified BCC s and SCC s, to identify factors causing the erroneous clinical interpretation and, therefore, minimize the morphologic overlap between BCC and SCC . Methods Retrospective study including histopathologically diagnosed BCC s or SCC s that had been clinically inversely diagnosed. Their dermatoscopic images were blindly evaluated for the presence of predefined criteria. Descriptive statistics were performed and univariate and multivariate predictors were calculated. Results A total of 68 cases were included, 41 of which were BCC s and 27 SCC s. Most tumours in both groups were non‐pigmented, ulcerated and displayed a polymorphous vascular pattern. The presence of erosions was positively associated to BCC (5.2‐fold higher odds, P  = 0.05), whereas scales/keratin masses were positively associated to SCC (3.7‐fold higher odds, P  = 0.07), although marginally not statistically significant. Conclusions Clinically misclassified BCC s and SCC s are usually non‐pigmented ulcerated tumours. Erosions and keratin masses/scales are more robust criteria as compared to vascular structures for the differential diagnosis between BCC and SCC .