Endoscopy: current state and future trends in tumor diagnosis

Gastrointestinal endoscopy has been significantly improved during the last decade. Tumors of less than 5 mm in diameter can now be detected by using high-resolution videoendoscopes. Additional in vivo staining allows better delineation and more precise identification of the lateral spreading of lesions. Today the missing of cancers in early stage is mainly due to lack of screening programs rather than technical limitations. Endoscopic mucosal resection of superficial lesions is primarily a diagnostic procedure to determine the need for surgery. However, it may be curative when histology proves a complete resection. Swallowable endoscopy capsules provide access to the entire small bowel. The capsule takes 2 images/second and transmits them to a recorder. After passage of the small bowel the 50,000 recorded images are reviewed on a computer. The capsule should not be used in patients with suspected intestinal stenosis. Endoscopic ultrasound (EUS) is an established procedure for the T- and N-staging of gastrointestinal tumors. With an accuracy rate of around 90%, this method is helpful for the therapeutic decision e.g. indication for operation. EUS cannot distinguish benign from malignant changes, particularly in focal pancreatic lesions. However, this drawback can be reduced with EUS-guided fine-needle aspiration cytology of the primary lesion or an accessible lymph node. At 7.5-20 MHz the gastrointestinal wall is visualized in 5 and more layers allowing for detailed staging of T1 tumors. 3D-EUS resolution is described to be better than 100 microns. Optical coherence tomography (OCT) with a resolution of 10-20 microns demonstrates tissue micro-architecture. Structures only seen in histology before are visualized real-time in vivo during endoscopy. However, the infiltration depth is only 1 mm and the method is still in the clinical experimental stage. Confocal microscopy has been recently adapted for endoscopy. Images from the first clinical evaluations already show single cells and nuclei. Cellular characteristics become visible and endoscopy is on the way towards optical biopsy.