Abstract: Objective: To investigate the diangostic value and safety of the endoscopic ultrasound guided fine needle aspiration biopsy(EUS-FNA) in mediastinal and retroperitoneal lymph node metastasis cancer.Methods: The data of 119 patients suspected by mediastinal and/or retroperitoneal lymph nodes tumor metastasis complicated with or without substance or hollow organ wall placeholder were retrospectively analyzed.A total of 187 lesions were treated with EUS-FNA,and puncture lymph nodes in 140 cases and puncture the wall of hollow organs or substance placeholder in 47 cases were implemented.The postoperative complications in all cases were observed,and the results of cytology and histology were followed up.Results: Among 119 cases,the sensitivity,specificity,positive predictive value,negative predictive value and accuracy of EUS-FNA in diagnosing the lymph nodes metastasis carcinoma were 92.5%,100.0%,100.0%,86.7% and 95.0%,respectively.The substance or hollow organ wall placeholder in 47 cases were found.The malignant carcinoma in 41 cases(including 35 cases of primary tumors and 6 cases of metastatic tumors),benign tumor in 4 cases and indefinite diagnosis in 2 cases were identified using EUS-FNA.According to post-operative observation,chest pain in 1 case,slight abdominal pain in 2 cases(including 1 cases complicated with transient fever) were identified,and the patients improved after symptomatic treatment.No bleeding and perforation were found.Conclusions: The pathological diagnosis of multi-site lesions can be obtained using EUS-FNA.EUS-FNA has clinical certain value in the diagnosis of mediastinal and retroperitoneal lymph nodes metastasis carcinoma,which is safe by real-time ultrasonography monitoring,and worthy of attention in clinic.