ULTRA-HIGH MAGNIFICATION ENDOSCOPY (ENDOCYTOSCOPY SYSTEM) FOR EXAMINATION OF ESOPHAGEAL LESIONS

Abstract

We report in detail the progress that has been made in the development and use of the endocytoscopy system (ECS), and introduce the ECS appearance of various esophageal lesions.

The first-generation ECS was developed in 2003 as an ultra-high magnification endoscope (fixed focus, probe) allowing magnification to the cell level. The latest (fourth-generation) ECS offers a hi-vision view with a consecutive increase in magnification to ×500. This ECS makes it possible to observe features at the “conventional endoscopy level”, “microvasculature level” and “cell level” through a gradual increase in magnification using a hand lever during the same examination.

For observation of cells using ECS, vital staining with toluidine blue, etc., is necessary. In the esophagus, cell staining can be observed just after spraying the dye into the esophageal lumen. After vital staining, it is possible to observe cells on the mucosal surface by bringing the lens of the ECS into contact with the target mucosa.

We propose a type classification to distinguish malignant lesions from benign lesions efficiently : (1) Type 1, surface epithelial cells have a low nucleus/cytoplasm (N/C) ratio and a low cell density. No nuclear abnormality is evident. (2) Type 2, there is a high nuclear density but no evident nuclear abnormality. No clear borders between cells are evident. (3) Type 3, evidently increased nuclear density and nuclear abnormality.

On the basis of in vivo observation, the sensitivity and specificity of ECS for malignant lesions by an endoscopist were 93.6％ and 94.6％, respectively, if Type 3 was considered malignant. With regard to a pathologist’s interpretation of the ECS images, the sensitivity and specificity for malignant lesions were 93.6％ and 98.8％, respectively. On the basis of ECS images, neither the endoscopist nor the pathologist was able to clearly distinguish regenerative squamous epithelium in gastroesophageal reflux disease and esophagitis after radiotherapy from esophageal cancer. In such cases, histological examination of biopsy specimens would be necessary in addition to ECS diagnosis.

ECS observation of esophageal lesions will facilitate “optical biopsy”, and allow omission of histological examination of biopsy specimens in many cases. However, as ECS observation is limited to observation of cells on the mucosal surface, this must be recognized as a limitation of this new technology.