Chromoendoscopy (that involves spraying of dyes over the colonic mucosa) combined with magnification has been utilized for polyp histology identification. Pit patterns on the surface of polyps described by Kudo et al have been shown to have a high diagnostic accuracy in differentiating the polyp types (18, 19). NBI, that is also referred to as "electronic chromoendoscopy" is another technique that has been evaluated for polyp histology identification by highlighting the superficial mucosal and vascular architecture (15, 20, 21). pCLE is another novel addition to the technologies aiming to accomplish in vivo histologic diagnosis with a high degree of accuracy. The pCLE system has three major components (Mauna Kea Technologies, Paris, France). The first is the confocal miniprobe made of approximately thirty thousand optical fibers bundled together and terminated by a distal microsystem. The images obtained have a lateral resolution of 1µm, an axial resolution of 10 µm and a maximum field of view of 240 µm. The depth of observation is from 55 to 65 µm. The miniprobe tip diameter is 2.5 mm and can be passed through the accessory channel of any standard endoscope. The second is the laser scanning unit (excitation wavelength - 488 nm) that combines the functions of laser light illumination and rapid laser scanning, enabling a frame rate up to 12 images per second and signal detection. The third is the control and acquisition software for real time image reconstruction, immediate sequences display and post-procedure analysis and editing tools. Once an area of interest (e.g. a polyp) is identified, 5 ml of 10% fluorescein sodium is injected intravenously; the confocal probe is passed through the accessory channel of the endoscope and placed against the lesion to obtain several high-quality images and video sequences. In a study by Buchner et al from the Mayo Clinic, Jacksonville, (22) this system was used to evaluate confocal images of 37 polyps from 25 patients in a blinded fashion without the knowledge of their histologic diagnosis or endoscopic appearance. The investigators developed the following criteria that were suggestive of neoplastic polyps: villiform pattern, nuclear characteristics - oval/irregular nuclear shape and increased number of nuclei. These features had a sensitivity of 82.6%, specificity of 92.9% and accuracy of 86.5% for the characterization of neoplastic polyps. Similarly, Meining et al (23) have also evaluated criteria for differentiating neoplastic from benign lesions in the colon with encouraging results.