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Maggiore Hospital, Bologna, Italy
Correspondence to: Marco Patelli, MD, FCCP, Unit of Thoracic Endoscopy and Pulmonology, Maggiore Hospital, Largo Nigrisoli 2, 40133 Bologna, Italy; e-mail: marco.patelli{at}ausl.bologna.it
To the Editor:
We read with great interest the article by Herth et al1 (January 2004), which reports the results of a randomized trial comparing conventional vs endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA) of mediastinal lymph nodes (LNs). This is a very intriguing study, in which the authors performed TBNA during flexible or rigid bronchoscopy, and separately randomized and analyzed the results of the TBNA procedures obtained from different LN stations. In a first group, they included exclusively the subcarinal nodes, since they are easily accessible by any method. In a second group, they included all the TBNAs performed in the following LN stations according to the American Thoracic Society classification2: 2 (right and left); 3, 4 (right or left); and 5. The conclusions and the comments of this study contain some very important issues for bronchoscopists who routinely perform TBNA, and therefore deserve a few comments.
The authors conclude that "EBUS guidance significantly increases the yield of TBNA in all lymph node stations except in the subcarinal one." However, the data as proposed in Table 2 of their study show that similar diagnostic yields were obtained by both conventional and EBUS-guided TBNA also in the lower paratracheal area (4 right, 4 left). By considering these data, it looks like blind TBNA procedures proved as effective as ultrasound-guided ones in those stations (4 right, 4 left, 7), among those accessible to TBNA, where the majority of metastasis from non-small cell lung cancer (NSCLC) occurs.34 This result is not surprising if one takes into account the fact that the above-mentioned LN areas (mainly 4R and 7) have been associated with very high (approximately 70%) diagnostic yields of conventional TBNA in several comprehensive studies in the settings of both malignant56 and benign diseases.7 A definite advantage was associated with ultrasound guidance only for TBNAs performed in LN stations (2, 3) less frequently involved by the metastatic spread of NSCLC, which is the most common indication to TBNA in clinical practice.8
The article also shows that 21 of 50 TBNA procedures in the non-subcarinal group were performed in the aortopulmonary window (APW), also called the subaortic station (station 5), which to the best of our knowledge is not accessible to TBNA. According to the American Thoracic Society LN map definition,2 the APW nodes "... are lateral to the ligamentum arteriosum or the aorta or the left pulmonary artery... " and are therefore not in contact with the airways. In a recent review9 on invasive mediastinal staging of NSCLC, it is stated that the possible ways to access the APW nodes are the following: anterior mediastinotomy (also known as the Chamberlain procedure), extended cervical mediastinoscopy, thoracoscopy, and transesophageal endoscopic ultrasound with fine-needle aspiration. Is it possible that these 21 TBNA procedures were performed in the left paratracheal area?
Another important aspect that is dealt with by Herth and colleagues is concerned with the significance of a TBNA aspirate yielding lymphocytes only, a finding basically meaning that the LN has been likely punctured.10 Interestingly, they observed that no patients with lymphocytes only on TBNA had a more specific diagnosis after subsequent surgical biopsy. We have proposed, albeit arbitrarily, that at least 30% of cellularity be composed of lymphocytes in order to consider adequate a TBNA cytology specimen.67 By using this quantitative cut-off value, two of nine adequate negative TBNA cytology specimens (23%) were subsequently shown to be false-negative at mediastinoscopy in a study on the role of TBNA in the mediastinal staging of NSCLC.6 Even more false-negative, lymphocyte-based TBNA aspirates can be observed in patients with sarcoid LNs, a condition in which the use of a 19-gauge histology needle makes it much easier to recover granulomas.7 By considering these data, we tend not to rely exclusively on an adequate negative TBNA cytology specimen—even in the presence of lymphocytes only—to rule out a more specific diagnosis mainly if the clinicoradiologic picture is evocative.
In conclusion, we think that EBUS can be a useful tool to guide TBNA in some specific settings, such as "difficult mediastinal LN areas" (mainly 2, 3, 4L) and small LN size (< 1 cm), although the technique is costly and requires a considerably long apprenticeship. For the time being, conventional TBNA has to be considered less costly, easier to learn, and offers similar yields in the LN stations more frequently involved by NSCLC, among those accessible to the technique.
References
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