Ultraviolet laser-induced autofluorescence distinction between malignant and normal urothelial cells and tissues
The aim of this study was to perform a preliminary evaluation of the diagnostic potential of laser-induced autofluorescence spectroscopy (LIAFS) for urothelial tumors, using fluorescence intensity ratios at different wavelengths. After testing three laser excitation wavelengths in normal and malignant bladder cell lines, 308 nm appeared to be the most promising wavelength since tow fluorescence bands were observed at 360 and 440 nm; these were attributed to tryptophan (Trp) and reduced nicotinamide adenine dinucleotide (NADH) respectively. This study was then performed on freshly removed normal bladder and bladder tumor specimens exclusively using the 308-nm excitation wavelength. The tumor spectra, regardless of stage and grade, were very similar to the malignant cell spectra. However, a marked reduction of overall intensity was observed for carcinoma in situ (CIS). Normal bladder mucosa exhibited a shift of the first fluorescence band to 380 nm, indicating an overlap of Trp urothelial cell emission and collagen fluorescence derived from the lamina propria. The intensity of the NADH emission band was markedly reduce in tumor tissues compared with normal mucosa, which could indicate different redox conditions in urothelial tumors. A fluorescence intensity ratio at 360 and 440 nm can accurately discriminate normal or inflammatory mucosa from all bladder tumors, including CIS. These findings support the use of LIAFS as a new diagnostic technique for occult urothelial tumors.