Background: Basal cell carcinoma (BCC) is the most common malignant skin tumour. An accurate preoperative margin assessment is important for complete surgical removal, as an incomplete excision with positive margins (R1) may require an additional procedure. An established clinical method for the evaluation of BCCs is dermatoscopy; however, an additional value of UV dermatoscopy for preoperative tumour delineation has so far not been sufficiently investigated. The aim of this thesis was therefore to examine whether BCCs would be delineated more precisely preoperatively using the UV dermatoscopy than with conventional dermatoscopy, and whether this might affect the clinical delineation of tumour margins in the future, particularly in the case of histologically incomplete excisions. Material and methods: A retrospective observational study was conducted including 49 histologically confirmed BCC lesions that were surgically treated at the Department of Dermatology and Venereology, LKH-University Hospital Graz, between 01 January 2024 and 31 January 2025. Four standardized dermatoscopic images were available for each lesion: 1) conventional cross-polarized, 2) conventional parallel-polarized, 3) UV cross-polarized, and 4) UV parallel-polarized. The image acquisition was performed using a DermLite DL5 in combination with an iPad mini. Three observers with different levels of experience and expertise (expert, resident, medical student) independently outlined the tumour margins on the preoperative images. Tumour areas were then measured pixel-based using the software ImageJ and subsequently converted into mm² using a custom-made Excel tool. The primary outcome was the histopathological resection status (R0 vs. R1). Difference in preoperatively delineated tumour area between conventional and UV dermatoscopy, the influence of the polarization mode, and interobserver variability were defined as the secondary of the study. An exploratory subtype analysis and a subgroup analysis of R1 lesions were also performed. Statistical analysis was carried out using descriptive statistics on the one hand and Wilcoxon signed-rank test and the Mann–Whitney U test on the other. Results: Across the entire cohort, UV dermatoscopy resulted in larger preoperatively delineated tumour areas than by using conventional dermatoscopy in five of six observer–polarization combinations. Statistically significant differences were found for HW in both polarization modes, for SM also in both modes, and for MZ in the parallel-polarized setting; only MZ delineated slightly larger areas using conventional dermatoscopy in the cross-polarized setting. Regarding the polarization mode, conventional dermatoscopy showed significantly broader tumour areas in the cross-polarized than in the parallel-polarized setting. This was seen for all three observers. Using UV dermatoscopy, by contrast, there was no statistical significance observed between the two polarization modes. Interobserver analysis demonstrated clear observer-dependent differences: on average, the largest tumour areas were delineated by HW, the smallest by MZ, and SM was usually in between. 16 out of the 49 lesions showed positive resection margins (R1). In this clinically relevant subgroup, lesions also tended to be delineated more broadly under UV dermatoscopy than under conventional dermatoscopy; for SM, statistical significance was found in both polarization modes and for HW in the parallel-polarized setting. However, the exploratory analysis of histological subtype revealed no significant subtype-dependent differences. Conclusions: The findings of this study suggest that UV dermatoscopy generally leads to broader preoperative tumour delineation in BCCs than conventional dermatoscopy. This tendency was also observed in lesions with histologically positive margins and therefore indicates the potential clinical benefit in preoperative surgical planning. When using conventional dermatoscopy, the polarization mode had a significant influence on tumour delineation, whereas this effect was not observed under UV dermatoscopy. At the same time, the data show that tumour delineation substantially depends on the individual observer interpretation. Therefore, first evidence was provided in this study, that UV dermatoscopy may represent a useful additive tool in the preoperative assessment of BCC. Due to the retrospective character and limited sample size, prospective studies should be done to validate its actual impact on the rate of incomplete excisions.
Ultraviolet dermatoscopy for the assessment of tumour margins in the preoperative diagnosis of basal cell carcinoma (BCC)
Mestel, S. J. (Autor/-in). 2026
Studienabschlussarbeit: Diplomarbeit