f - fluorodeoxyglucose positron emission tomography / computed tomography ( fdg - pet / ct ) has been used in the diagnosis of lung cancer and plays a crucial role in distinguishing benign from malignant pulmonary and lymph node lesions . non - neoplastic lesions with excessive f - fdg uptake are typically those with a large number of macrophages and lymphocytes , such as tuberculosis and other granulomas ( 2 ) . thus , tissue confirmation is recommended even when the fdg - pet / ct findings in regional lymph nodes are positive ( 3 ) . endobronchial ultrasound - guided transbronchial needle aspiration ( ebus - tbna ) is a minimally invasive procedure with a high diagnostic yield for mediastinal lymph node staging , not only in patients with lung cancer but also in those with other pulmonary and mediastinal diseases ( 4,5 ) . the american college of chest physicians recommends a needle technique [ ebus - needle aspiration , esophageal endoscopic ultrasound - needle aspiration ( eus - na ) or combined ebus / eus - na ] over surgical staging as a best first examination in patients in whom n2 and n3 involvement is suspect , based on either discrete mediastinal lymph node enlargement or fdg uptake ( 6 ) . however , the superiority of ebus - tbna over fdg - pet / ct for preoperative n1/n2 staging has yet to be convincingly documented . here , we describe our experience using ebus - tbna in lung cancer patients with n1/n2 disease detected on fdg - pet / ct . the medical records of 50 consecutive lung cancer patients with n1/n2 disease on fdg - pet / ct were retrospectively evaluated . between november 2012 and april 2015 , all patients with positive lymph nodes on fdg - pet / ct underwent ebus - tbna for further diagnosis of pathological lymph nodes . ebus - tbna and fdg - pet / ct were performed at okayama university hospital and okayama diagnostic imaging center , respectively . a maximum standardized uptake value ( suvmax ) > 2.5 was defined as a positive result signifying malignancy . the study was approved by the institutional ethics committee of okayama university hospital ( no . 1508 - 019 ) . blood glucose was measured in fasted ( 5 h ) patients to ensure a level of < 140 mg / dl . patients were then administered an intravenous injection of 3.7 mbq fdg / kg ( 1.0  10 ci / kg ) body weight and asked to rest in a reclining chair until the scan , to minimize muscle consumption of fdg . pet image acquisition using an integrated pet / ct scanner ( biograph ls / sensation16 , siemens , munchen , germany ) began 90 min after the injection of fdg . first , a total - body low - dose ct scan was acquired to calculate the attenuation correction . the standardized protocol was as follows : 140 kv , 1214 mas , a tube - rotation time of 0.5 s per rotation , a pitch of 0.8 , a section thickness of 3 mm and a scan field ranging from the head to the mid - thigh level ( 78 bed positions , 2.4 min per table position ) . the pet images were reconstructed with an ordered - subset expectation maximization iterative reconstruction algorithm . integrated , coregistered pet / ct images were obtained using a workstation ( pet viewer , aze , tokyo , japan ) , which enabled image fusion and analysis . expert visual interpretation of the images by radiologists specialized in pet / ct was obtained before bronchoscopic examination of the patients . in expert visual interpretation by radiologists , the clinical applicability of lymph node enlargement in ct is > 10 mm short axis diameter . receiver operating characteristic ( roc ) curves analysis was used by stata / seversion 11.0 software ( college station , tx , usa ) . conventional flexible bronchoscopy ( bf-260 bronchovideoscope , olympus ; tokyo , japan ) was performed for observational purposes , using a siliconized , uncuffed tracheal tube with an inner diameter of 7.5 mm ( portex ; smiths medical , st . ebus - tbna was then performed using a convex - probe ebus bronchoscope ( bf - uc260f - ol8 , olympus ; tokyo , japan ) . prior to the latter procedure , the patients were administered 25 mg of hydroxyzine pamoate by intramuscular injection . of note , 5 ml of 2% lidocaine was first sprayed into the pharynx and then administered again through the working channel during the examination . the bronchoscope was inserted orally in patients under conscious sedation induced by midazolam or a combination of midazolam and fentanyl . patients were monitored by electrocardiogram , pulse oximetry and blood pressure without the presence of an anesthesiologist . mediastinal lymph nodes accessible by ebus ( stations 2 , 4 and 7 ) and hilar lymph nodes ( stations 10 and 11 ) were examined to identify those with a suvmax > 2.5 . the aspirated material was pushed out of the puncture needle , smeared on a watch glass and then evaluated immediately by an on - site cytopathologist using bioevaluator ( murazumi industrial co. ltd , osaka , japan ) ( 8) . more than half of the smears were stained using hemacolor rapid staining ( promiclos ; tokyo , japan ) . the remaining samples were fixed in 10% formalin , paraffin - embedded , stained with papanicolaou stain and evaluated histologically . statistical analysis was performed using microsoft office excel 2007 ( microsoft japan corporation , tokyo , japan ) . comparisons between the two groups were made using unpaired student 's t - test . a p value < 0.05 was considered to indicate statistical significance . the medical records of 50 consecutive lung cancer patients with n1/n2 disease on fdg - pet / ct were retrospectively evaluated . between november 2012 and april 2015 , all patients with positive lymph nodes on fdg - pet / ct underwent ebus - tbna for further diagnosis of pathological lymph nodes . ebus - tbna and fdg - pet / ct were performed at okayama university hospital and okayama diagnostic imaging center , respectively . a maximum standardized uptake value ( suvmax ) > 2.5 was defined as a positive result signifying malignancy . the study was approved by the institutional ethics committee of okayama university hospital ( no . 1508 - 019 ) . blood glucose was measured in fasted ( 5 h ) patients to ensure a level of < 140 mg / dl . patients were then administered an intravenous injection of 3.7 mbq fdg / kg ( 1.0  10 ci / kg ) body weight and asked to rest in a reclining chair until the scan , to minimize muscle consumption of fdg . pet image acquisition using an integrated pet / ct scanner ( biograph ls / sensation16 , siemens , munchen , germany ) began 90 min after the injection of fdg . first , a total - body low - dose ct scan was acquired to calculate the attenuation correction . the standardized protocol was as follows : 140 kv , 1214 mas , a tube - rotation time of 0.5 s per rotation , a pitch of 0.8 , a section thickness of 3 mm and a scan field ranging from the head to the mid - thigh level ( 78 bed positions , 2.4 min per table position ) . the pet images were reconstructed with an ordered - subset expectation maximization iterative reconstruction algorithm . integrated , coregistered pet / ct images were obtained using a workstation ( pet viewer , aze , tokyo , japan ) , which enabled image fusion and analysis . expert visual interpretation of the images by radiologists specialized in pet / ct was obtained before bronchoscopic examination of the patients . in expert visual interpretation by radiologists , the clinical applicability of lymph node enlargement in ct is > 10 mm short axis diameter . receiver operating characteristic ( roc ) curves analysis was used by stata / seversion 11.0 software ( college station , tx , usa ) . conventional flexible bronchoscopy ( bf-260 bronchovideoscope , olympus ; tokyo , japan ) was performed for observational purposes , using a siliconized , uncuffed tracheal tube with an inner diameter of 7.5 mm ( portex ; smiths medical , st . ebus - tbna was then performed using a convex - probe ebus bronchoscope ( bf - uc260f - ol8 , olympus ; tokyo , japan ) . prior to the latter procedure , the patients were administered 25 mg of hydroxyzine pamoate by intramuscular injection . of note , 5 ml of 2% lidocaine was first sprayed into the pharynx and then administered again through the working channel during the examination . the bronchoscope was inserted orally in patients under conscious sedation induced by midazolam or a combination of midazolam and fentanyl . patients were monitored by electrocardiogram , pulse oximetry and blood pressure without the presence of an anesthesiologist . mediastinal lymph nodes accessible by ebus ( stations 2 , 4 and 7 ) and hilar lymph nodes ( stations 10 and 11 ) were examined to identify those with a suvmax > 2.5 . the aspirated material was pushed out of the puncture needle , smeared on a watch glass and then evaluated immediately by an on - site cytopathologist using bioevaluator ( murazumi industrial co. ltd , osaka , japan ) ( 8) . more than half of the smears were stained using hemacolor rapid staining ( promiclos ; tokyo , japan ) . the remaining samples were fixed in 10% formalin , paraffin - embedded , stained with papanicolaou stain and evaluated histologically . statistical analysis was performed using microsoft office excel 2007 ( microsoft japan corporation , tokyo , japan ) . comparisons between the two groups were made using unpaired student 's t - test . a p value < 0.05 was considered to indicate statistical significance . the median age of the 34 males and 16 females was 61 ( range , 3484 ) years . the pathological diagnoses were as follows : 36 adenocarcinomas , 8 squamous - cell carcinomas , 3 small - cell carcinomas and 3 large - cell neuroendocrine carcinomas . the lymph nodes ( n = 61 ) were subsequently aspirated with a median of 2 ( range , 15 ) attempts per node and consisted of 29 subcarinal , 21 right lower paratracheal , 6 left lower paratracheal , 4 right hilar nodes and 1 upper paratracheal node ( table  2 ) . the mean size of the enlarged lymph nodes , measured over the long axis using ct imaging , was 23.4 ( range , 10.445.7 ) mm . during ebus - tbna , 4 patients experienced fever , which was easily managed . necrotic or cystic areas in 10 of 61 lymph nodes were punctured , and the patients did not experienced fever or severe complications . device breakage was not observed during this study . the use of ebus - tbna allowed for definitive diagnoses in 39 patients ( 31 adenocarcinomas , 2 squamous - cell carcinomas , 3 small - cell carcinomas and 3 large - cell neuroendocrine carcinomas ) . the ebus - tbna samples in 9 of these patients contained abundant lymphocytes , and all 9 underwent a thoracotomy . expert visual interpretation of the pet / ct images obtained from these patients was non - specific lymphadenopathy in five cases . the ebus - tbna samples in the remaining 2 of the 11 patients were insufficient for evaluation . in both cases , cancer metastasis was finally diagnosed , because the lymph nodes responded to chemoradiotherapy with a reduction in size . thus , ebus - tbna samples from 48 of the 50 patients were diagnostically sufficient ( supplementary data , table s1 ) . table  1.patient characteristicscharacteristicvalue ( range)number of patients50male / female , n 
 34/16median age ( range ) , years61 ( 3484)pathological diagnosis , n 
 adenocarcinoma36  squamous - cell carcinoma8  small - cell carcinoma3  large - cell neuroendocrine carcinoma3 
 table  2.characteristics of the punctured lymph nodescharacteristicvalue ( range)number61enlarged lymph node stations ( 4r/4l/7/11/2r ) , n 
 21/6/29/4/1longest diameter ( range ) , mm23.4 ( 1045)diagnosis by ebus - tbna , n 
 adenocarcinoma31  squamous - cell carcinoma2  small - cell carcinoma3  large - cell neuroendocrine carcinoma3  indefinite11mean suvmax ( range)7.09 ( 2.9026.9 )  positive nodes by ebus - tbna ( n= 47)11.35 ( 2.9026.9 )  negative nodes by ebus - tbna or thoracotomy ( n= 12)4.75 ( 3.117.14 )  uncertain nodes by ebus - tbna ( n= 2)5.79 ( 2.998.79)ebus - tbna , endobronchial ultrasound - guided transbronchial needle aspiration ; suv , standardized uptake value.lymph node stations were defined as follows : 4l , left lower paratracheal node ; 4r , right lower paratracheal node ; 7 , subcarinal nodes ; 11 , n1 nodes ; 2r , upper paratracheal node . patient characteristics characteristics of the punctured lymph nodes ebus - tbna , endobronchial ultrasound - guided transbronchial needle aspiration ; suv , standardized uptake value . lymph node stations were defined as follows : 4l , left lower paratracheal node ; 4r , right lower paratracheal node ; 7 , subcarinal nodes ; 11 , n1 nodes ; 2r , upper paratracheal node . the mean suvmax of the lymph nodes from the 50 patients was 7.09 ( range , 2.9026.9 ) . the mean suvmax of the negative lymph nodes diagnosed by ebus - tbna or thoracotomy [ 4.75 ( range , 3.117.14 ; n = 12 ) ] was significantly lower than that of the positive lymph nodes diagnosed by ebus - tbna alone [ 11.35 ( range , 2.9026.9 ; n = 47 ) ] ( p < 0.05 ) . the suvmax of the lymph nodes from the two patients with insufficient material was 2.99 and 8.79 . we showed sensitivity , specificity , positive predict value , negative predict value and accuracy by ebus - tbna and pet - ct were shown in supplementary data , table s2 . although suvmax > 2.5 was selected for cut - off point in this study , roc curve of pet / ct according to variable suvmax was described in supplementary data , figure s1 . in order to predict a more favorable cut - off point of suvmax than 2.5 , we calculated the diagnostic accuracy ( supplementary , data , table s3 ) . when the cut - off point was set to 4.31 , the diagnostic accuracy was 83.61% with sensitivity of 89.80% and specificity of 58.33% . the prediction cut - off point of suvmax may depend on the histological type . since most predominant histology was adenocarcinoma , we performed roc curve analysis ( supplementary data , figure s2 ) and calculated diagnostic accuracy , sensitivity , and specificity ( supplementary data , table s4 ) in adenocarcinoma histology . the most favorable cut - off point was 4.31 with diagnostic accuracy of 80.00% , sensitivity of 86.84% and specificity of 58.33% . a 58-year - old male with lung cancer in the right middle lobe had mediastinal lymph node enlargement with fdg uptake . expert visual interpretation resulted in a diagnosis of metastasis ; however , the ebus - tbna samples contained abundant lymphocytes without malignant cells . figure  1.a 58-year - old male patient with lung cancer in the right middle lobe had mediastinal lymph node enlargement on computed tomography ( ct ) ( a and b ) , positron emission tomography / computed tomography ( pet / ct ) ( c ) and endobronchial ultrasound ( d ) imaging . a 58-year - old male patient with lung cancer in the right middle lobe had mediastinal lymph node enlargement on computed tomography ( ct ) ( a and b ) , positron emission tomography / computed tomography ( pet / ct ) ( c ) and endobronchial ultrasound ( d ) imaging . although this was a small and retrospective study , our experience has shown that ebus - tbna is useful for diagnosing n1/n2 disease detected on fdg - pet / ct . the superiority of ebus - tbna over fdg - pet / ct for preoperative n1/n2 staging was previously suggested ( 9,10 ) , although it could not be definitively documented . fdg - pet / ct plays a crucial role in detecting mediastinal lymph node involvement in patients with potentially resectable lung cancer . however , its sensitivity and specificity are too low for mediastinal staging ( 0.770.81 and 0.790.90 , respectively ) ( 11 ) . our results , reported in table  2 , are in agreement with this conclusion , as only 78% ( 39/50 ) of the study patients with n1/n2 disease detected on fdg - pet / ct ( suvmax > 2.5 ) were similarly diagnosed by ebus - tbna , whereas the 9 patients with n2 disease on fdg - pet / ct underwent surgical treatment based on the number of normal lymphocytes in their ebus - tbna samples , which indicated benign lymphadenopathy . the utility of ebus - tbna for preoperative lymph node staging in patients with lung cancer is widely accepted , and the procedure is at least as effective as mediastinoscopy for the mediastinal staging of non - small - cell lung cancer , given its high sensitivity ( 90% ) and specificity ( 100% ) ( 1214 ) . in this study , ebus - tbna samples of 96% ( 48/50 ) of the patients contained a sufficient number of lymphocytes to allow a diagnosis . based on expert visual interpretation of the fdg - pet / ct images , non - specific lymphadenopathy was diagnosed in five of the nine patients whose ebus - tbna samples showed normal lymphocytes without malignant cells . thus , ebus - tbna can be considered as a diagnostic tool regardless of expert visual interpretation . the first japanese nationwide survey describing complications associated with the use of ebus - tbna revealed severe infections and frequent device breakages ( 15 ) . although necrotic or cystic areas in 10 of 61 lymph nodes were punctured , we did not experience fever and severe complications in such cases . the threshold of suvmax for positive lymph nodes has yet to be definitively defined . in our patients , positive lymph nodes had a significantly higher mean suvmax than negative lymph nodes , as subsequently determined by ebus - tbna ( table  2 ) . we have also seen patients with negative mediastinal findings ( suvmax < 2.5 ) on fdg - pet / ct whose ebus - tbna samples included malignant cells . thus , studies aimed at determining the threshold suvmax to identify those patients who are candidates for ebus - tbna would be highly valuable . among the many factors that contribute to the suv are body mass including fat tissue ( 16 ) , blood glucose level ( 17 ) , time of the examination in relation to administration of the marker and the size of the lesion ( 18 ) . recently , several different objective criteria for fdg - pet / ct scan interpretation were proposed : suvmax lymph node / suvmax primary lung malignancy ( 19 ) , suvmax lymph node / suv average liver ( 20 ) , suvmax lymph node / suvmax liver ( 21 ) , and suvmax lymph node / suvmax blood pool ( 22 ) . ( 11 ) reported that the sensitivity and specificity of fdg - pet / ct were related not only to the fdg dose but also to other factors . since most favorable predictive cut - off point of suvmax in not only all histology but also adenocarcinoma alone was 4.31 in this study , we should evaluate the value prospectively . the cut - off point or the other objective criteria for pet / ct scan interpretation ( 1922 ) might be useful for estimating lymph nodes which are difficult to obtain by ebus - tbna . further prospective studies will aid in determining the objective criteria for fdg - pet / ct scan interpretation and therefore whether n1/n2 staging with ebus - tbna is more accurate . ebus - tbna may be useful in classifying benign and malignant n1/n2 disease detected on fdg - pet / ct and should be considered for accurate staging in patients with lung cancer and lymph node involvement . funding to pay the open access publication charges for this article was provided by the ministry of education , culture , sports , science , and technology , japan ( 15k21185 ) .
objectiveendobronchial ultrasound - guided transbronchial needle aspiration is of diagnostic value in hilar / mediastinal ( n1/n2 ) lymph node staging . 
 we assessed the utility of endobronchial ultrasound - guided transbronchial needle aspiration in lung cancer patients with n1/n2 lymph nodes detected on 18f - fluorodeoxyglucose positron emission tomography / computed tomography.methodsfifty lung cancer patients with n1/n2 disease on 18f - fluorodeoxyglucose positron emission tomography / computed tomography underwent endobronchial ultrasound - guided transbronchial needle aspiration for pathological lymph nodes between november 2012 and april 2015 . 
 the diagnostic performance of endobronchial ultrasound - guided transbronchial needle aspiration , lymph node site and size , number of needle passes and complications were evaluated retrospectively from patients ' medical records . 
 malignancy was defined as a maximum standardized uptake value ( suvmax ) > 2.5.resultsthe median longest diameter of the 61 lymph nodes ( 29 subcarinal , 21 right lower paratracheal , 6 left lower paratracheal , 4 right hilar and 1 upper paratracheal ) was 23.4 mm ( range : 10.445.7 ) ; the median number of needle passes was 2 ( range : 15 ) . 
 there were no severe complications . 
 a definitive diagnosis was made by endobronchial ultrasound - guided transbronchial needle aspiration in 39 patients ( 31 adenocarcinomas , 3 small - cell carcinomas , 2 squamous - cell carcinomas , 3 large - cell neuroendocrine carcinomas ) . in the remaining 11 patients , 
 the diagnosis was indefinite : insufficient endobronchial ultrasound - guided transbronchial needle aspiration material was collected in two patients and non - specific lymphadenopathy was confirmed by endobronchial ultrasound - guided transbronchial needle aspiration or thoracotomy in the other nine patients . 
 the mean lymph node suvmax was 7.09 ( range : 2.9026.9 ) and was significantly higher in true - positive than in false - positive nodes ( p < 0.05 , t - test ) . 
 non - specific lymphadenopathy was diagnosed by expert visual interpretation of 18f - fluorodeoxyglucose positron emission tomography / computed tomography images in five of the nine patients.conclusionendobronchial ultrasound - guided transbronchial needle aspiration accurately diagnoses n1/n2 disease detected on 18f - fluorodeoxyglucose positron emission tomography / computed tomography .