Magnification endoscopy in esophageal squamous cell carcinoma: a review of the intrapapillary capillary loop classification.

Recent developments in image-enhancement technology have enabled clear visualization of the microvascular structure of the esophageal mucosa. In particular, intrapapillary capillary loops (IPCLs) are observed as brown loops on magnification endoscopy with narrow-band imaging (NBI). IPCLs demonstrate characteristic morphological changes according to the structural irregularity of esophageal epithelium and cancer infiltration, summarized in the IPCL classification. In this review, the process from the first endoscopic description of IPCLs to the eventual development of the IPCL classification is described and discussed, particularly focusing on early stage squamous cell carcinoma of the esophagus.