Esophagus: The Japan Esophageal Society (JES) Classification

Predicting invasion depth of superficial esophageal squamous cell carcinoma is crucial in determining the precise indication for endoscopic resection (ER) because the rate of lymph node metastasis increases in proportion to the invasion depth of the carcinoma. Previous studies have shown a close relationship between microvascular patterns observed by magnifying endoscopy and invasion depth of the superficial carcinoma. Although there were two major classifications, Inoue and Arima, the Japan Esophageal Society (JES) integrated the two classifications and simplified it and developed a new magnifying endoscopic classification for the characterization and predicting invasion depth of superficial esophageal squamous cell carcinomas (SESCCs). This is essential for developing a treatment strategy for SESCC, in particular the indication for ER. Therefore, in this classification, morphological types of microvessels are classified into two categories of noncancerous [normal epithelium, inflammation, and intraepithelial neoplasia (IN)] and cancerous (SCC) lesions. The cancerous types of microvessels corresponding to SESCCs are subclassified into three groups based upon an indication for ER as follows: an absolute indication type (T1a-EP or T1a-LPM), a relative indication type (T1a-MM/SM1: tumor invades the submucosa to a depth of 200 μm or less from the muscularis mucosa), and a contraindication type (T1b-SM2: tumor invades the submucosa to a depth more than 200 μm). Diagnostic criteria of the JES classification are based on the degree of microvascular irregularity in the target lesion observed by magnifying endoscopy. Intrapapillary capillary loops (IPCL) are a basic unit of microvasculature in the stratified squamous epithelial layer. The microvascular irregularity is evaluated for the presence or absence of each of the following morphological factors: weaving (i.e., tortuosity), dilatation, irregular caliber, and different shape (i.e., various shapes). Microvessels are classified as type A if they have three or fewer factors (i.e., without severe abnormality; ◘ Fig. 1a) and type B if they have all four (i.e., with severe abnormality). Type B is then subclassified into B1, B2, and B3 (◘ Fig. 1b–d, respectively) based on the running pattern or degree of dilatation of severely irregular microvessels. The definitions and schemas of type A and B vessels and predicted histology of invasion depth by type B vessels are summarized in ◘ Table 1. A large validation study showed high overall accuracy (90.5%) of type B vessels of the JES classification. The most important auxiliary criterion in the JES classification is avascular area (AVA). AVA is defined as a low or no vascularity area surrounded by all subtypes of type B microvessels including B1 vessels. Diameters of AVA are positively correlated with sizes of histological cancer nest and the histological invasion depth of SESCC. Small (<0.5 mm), middle (0.5 ≤< 3 mm), and large (≤3 mm) AVA are suggestive of T1a-EP/LPM, T1a-MM/T1b-SM1, and T1b-SM2, respectively. A key point to note is that any types of AVA (small, middle, and large) surrounded by B1 vessels are suggestive of T1a-EP or T1a-LPM SCC.