ELN and cancer: Oral tissue irradiated with any blue light at the wavelength of 400–460 nm excites endogenous fluorophores such as keratin, collagen, elastin, and NADH to emit green light (500–520 nm). The degree of emission of green light decrease and appears as a black spot as dysplasia progression to cancer due to an increase in hemoglobin, porphyrins, and melanin, which tends to absorb the blue incident light, reducing the emission of green light