Fig. 4From: Current advances in noninvasive methods for the diagnosis of oral squamous cell carcinoma: a reviewAutofluorescence-based diagnostic technique. Apple green fluorescence (510 nm) is visible in healthy tissues under blue light at 400–460 nm, whereas malignant tumors lose their autofluorescence. This is related to the filtering effect, autofluorescence of collagen cross-links, and redox ratio [52]Back to article page