Abstract: A system characterizes tissue using fluorescence spectroscopy, such as light-induced fluorescence. Native fluorescence (“autofluorescence”) from endogenous tissue without requiring fluorescence-enhancing agents is used to distinguish between normal tissue, hyperplastic tissue, adenomatous tissue, and adenocarcinomas. The system provides endoscopic image enhancement for easy location of a tissue site for optical biopsy tissue characterization. The system allows the use of an integrated endoscopic diagnosis and treatment device for immediate diagnosis and treatment without interchanging equipment and relocating the tissue site. The system is also integrated with existing endoscopy equipment for initiating and displaying the diagnosis. The system provides an adjunctive tool to histopathological tissue classification or, alternatively, further treatment is based on the optical biopsy system diagnosis itself.