The Japanese Classification of Esophageal Cancer, 12th Edition, Part II, provides updated guidelines for the diagnosis and treatment of esophageal cancer. It includes detailed terminology, definitions, and classification criteria for various tumor types, including squamous cell carcinoma, adenocarcinoma, and other malignant tumors. The classification also defines Barrett's esophagus and its histological subtypes, as well as the esophagogastric junction (EGJ) and its role in cancer staging. The document outlines the staging system, which is based on the depth of tumor invasion (T), lymph node involvement (N), and distant metastasis (M). It also includes response evaluation criteria for radiotherapy and chemotherapy, such as RECIST, and describes the histological classification of tumors, including benign and malignant epithelial neoplasia, lymphoid tumors, and non-epithelial tumors. The classification emphasizes the importance of endoscopic evaluation, surgical resection, and multimodal treatment approaches. It also provides detailed guidelines for the treatment of esophageal cancer, including endoscopic resection, surgical resection, stenting, and radiotherapy. The document aims to standardize the diagnosis and treatment of esophageal cancer in Japan, ensuring consistency and accuracy in clinical practice.The Japanese Classification of Esophageal Cancer, 12th Edition, Part II, provides updated guidelines for the diagnosis and treatment of esophageal cancer. It includes detailed terminology, definitions, and classification criteria for various tumor types, including squamous cell carcinoma, adenocarcinoma, and other malignant tumors. The classification also defines Barrett's esophagus and its histological subtypes, as well as the esophagogastric junction (EGJ) and its role in cancer staging. The document outlines the staging system, which is based on the depth of tumor invasion (T), lymph node involvement (N), and distant metastasis (M). It also includes response evaluation criteria for radiotherapy and chemotherapy, such as RECIST, and describes the histological classification of tumors, including benign and malignant epithelial neoplasia, lymphoid tumors, and non-epithelial tumors. The classification emphasizes the importance of endoscopic evaluation, surgical resection, and multimodal treatment approaches. It also provides detailed guidelines for the treatment of esophageal cancer, including endoscopic resection, surgical resection, stenting, and radiotherapy. The document aims to standardize the diagnosis and treatment of esophageal cancer in Japan, ensuring consistency and accuracy in clinical practice.