Histopathological characteristics of an oral epithelial dysplasia model in rats showing a negative reaction to fluorescence visualization

Vital staining has long been used to delineate the horizontal margins for resection in oral squamous cell carcinoma and in oral epithelial dysplasia (OED). In recent years, fluorescence visualization (FV), a simple and non-invasive technique, has been used to identify resection margins. However, FV occasionally fails to detect OED. The purpose of this study is to investigate why lesions are not detected using FV and to evaluate their histopathology. The tongues of an OED rat model were examined using FV, and the obtained images were objectively evaluated by quantifying the fluorescence intensity (FI) through image analysis software. Hematoxylin-eosin and immunohistochemical staining were performed to characterize FV loss (FVL) and FV retention (FVR). Some OED lesions were recognized through FVR. In FVL, the CD31-positive rate was higher than in FVR, and the CD31-positive rate negatively correlated with FI. In contrast, a positive correlation was observed between FI and the thickness of the epithelial layer. Multiple regression analysis suggested that the CD31-positivity rate and epithelial thickness may be involved in FI. These findings suggest that the accuracy of FV detection is influenced by multiple factors, including angiogenesis and epithelial layer thickness. Therefore, a combination of various testing methods should be considered.