Objective To investigate the diagnostic value of EBUS imaging features for metastatic mediastinal/hilar lymph node enlargement in lung cancer.Methods The lung cancer patients with a pathological diagnosis and without preoperative anti-tumor treatment who got the EBUS-TBNA examination from October 2009 to September 2011 were retrospectively analysis.422 lung cancer patients with 683 mediastinal / hilar lymph nodes were enrolled in this study,including 335 males and 87 females; the median age is 61 years old (range 24-82),EBUS lymph node ultrasound image and the final pathological or follow-up results were compared by the statistical analysis.Homogeneity in the lymph node EBUS image feature was defined as:uniform echo in the ultrasound images,cortex existed in the peripheral areas,medulla existed in lymph central with a slightly stronger echo and represent as a small strip.Heterogeneity was defined as: the ultrasound image was defined as uneven echo involved with coagulation necrosis sign,which was the hypoechoic areas without blood flow in the lymph nodes and represent no blood flow in the CDPI mode.The coagulation necrosis was associated with necrosis within the lymph node.In addition,if the CNS region occupied more than 11％ of the entire lymph node in a complete lymph node or just a part of huge lymph nodes in the EBUS imaging window frame,we also regard it as heterogeneity.If a complete lymph node was seen in the EBUS imaging window frame,we measured the longest diameter to the long axis and its vertical maximum diameter to the short axis.If the lymph node was huge and extended the EBUS imaging window frame,we measured the longest diameter in the frame as the long axis of its vertical maximum diameter to be the short axis.As to the EBUS-TBNA negative lymph nodes,we regarded it was malignant lymph node if the diameter of the lymph node increased by 20％ in the patients who did not received any chemotherapy or radiotherapy or the diameter of the lymph node increased or decreased by 20％ in the patients who received any chemotherapy or radiotherapy six month later in the chest enhanced CT scan,otherwise,it was identified as benign lymph node.We used the RECIST 1.1 solid tumors criteria to evaluate the efficacy of the chemotherapy.Results 422 patients were enrolled this study including 93 squamous carcinomas,137 adenocarcinomas,97 small cell lung cancer,42 poorly differentiated non-small cell lung cancer,29 adenosquamous carcinoma and 24 other malignant tumors (including large cell carcinoma,sarcomatoid carcinoma,carcinoid tumors,etc).The sensitivity of the EBUS-TBNA was 93.8％ (396/422).The diagnostic methods and results in the 683 lymph nodes were as the following: 506/683 (74.1％) was confirmed as cancer by the EBUS-TBNA while 177/683 (25.9％) was diagnosed as benign disease.Among these,32/683 (4.7％) was confirmed as cancer and 57/683 (8.3％)was confirmed as benign disease by surgery,9/683 (1.3％) was confirmed as cancer and 79/683 (11.6％) was confirmed as benign disease by the method of follow-up.the sensitivity for the EBUS-TBNA to be malignant was 506/547 (92.5 ％),specificity was 136/136 (100％),positive predictive value was 506/506 (100％),negative predictive value was 136/177(76.8％) and accuracy was 642/683 (94.0％).The short axis diameter in the 683 lymph nodes ranged from 0.40cm to 4.60cm with an average diameter of (1.58 ± 0.68) cm.Among them,the short axis diameter in the malignant lymph node was (1.75 ± 0.63) cm,and in the benign lymph nodes was (0.92 ± 0.40) cm.527 lymph nodes presented heterogeneity under the ultrasound imaging,in which,519/527 (98.5 ％)were malignant lymph nodes.While,156 lymph nodes presented homogeneity and 28/156 (17.9％) were malignant lymph nodes (x2 =489.5,P ＜0.01).In the heterogeneous lymph node with a short axis diameter more than 1.0cm,the sensitivity to be malignant was 89.4％,specificity was 100％ and accuracy was 89.6％.In the homogeneous lymph node with a short axis diameter less than 0.8cm,the sensitivity to be benign was 43.8％,specificity was 67.8％ and accuracy was 48.1％.Conclusion EBUS-TBNA is new biopsy method for the mediastinal / hilar lymph node.The classification based on EBUS imaging-based lymph node ultrasound image features was helpful to identify the procedure for the diagnostic purposes and could help to distinguish the benign or malignant mediastinal / hilar lymph node in lung cancer patients.