Towards Accurate Breslow Measurements: Mitigating Issues in Histopathological Imaging

Background: Breslow thickness is a key prognostic parameter in the staging of cutaneous melanoma, but its manual measurement is affected by operator dependency and the com-plex morphology of the epidermis. Identifying both the deepest melanocyte and the correct perpendicular path to the epidermal surface can be challenging, especially in highly ir-regular tissues. Methods: This study investigates a more robust estimation of Breslow thickness through the development of a semi-automated Computer Vision–based software. Inter-operator variability was assessed by comparing measurements performed by seven histo-pathologists on 40 Whole Slide Images of non-ulcerated pT1a melanomas with Breslow thickness below 0.8 mm. Results: The agreement between human measurements and AI results was evaluated. Sig-nificant variability in the orientation of the measurement segments was observed, high-lighting the difficulty for human operators in identifying the correct perpendicular direc-tion. A linear relationship was found between angular variance and variance in Breslow thickness values, linking epidermal irregularity to increased measurement uncertainty. Conclusions: Overall, statistically significant differences were observed between the AI system and five of the seven operators, indicating a general tendency among experts to overestimate Breslow thickness.