The goal of this observational study is to learn about in describe participant population. The main questions it aims to answer are:

• What are the risk factors of postoperative pulmonary infection in patients with esophageal cancer？
• Whether we could establish a clinical prediction model to provide basis for early clinical intervention or not? Participants will describe the main tasks participants will be asked to do, treatments they'll be given and use bullets if it is more than 2 items. If there is a comparison group: Researchers will compare insert groups to see if insert effects.

Data were collected from the electronic medical records of Xijing Hospital. Each record is entered by two team members working simultaneously to ensure data accuracy.

Inclusion Criteria:

• Diagnosis of esophageal cancer;
• Radical resection of tumor for the first time;
• No distant metastasis was observed in preoperative examination

Exclusion Criteria:

• Patients with preoperative pulmonary infection or symptoms of pulmonary infection;
• Patients with tracheal intubation assisted ventilation before surgery;
• Patients with preoperative lung imaging changes or abnormal white blood cells in blood routine;
• Patients undergoing emergency surgery;
• Patients with other cancers;
• Patients with incomplete clinical data.

From January 2016 to December 2021, patients with esophageal cancer were hospitalized for surgery in the Department of Gastroenterology, Xijing Hospital.