What is the best technique for performing endoscopic ultrasound guided trans-esophageal fine needle aspiration of mediastinal lymph nodes?

Purpose: Trans-esophageal real-time endoscopic ultrasound (EUS) guided fine needle aspiration (FNA) has emerged as an important technique for sampling of mediastinal lymph nodes. However, it is unclear as to which is the best technique for performing EUS guided FNA. The purpose of this study was to compare the yield of EUS guided FNA of mediastinal lymph nodes with different techniques. Methods: A 2 cm mediastinal lymph node was dissected from an autopsy. A 21 gauge needle, which is used clinically for EUS guided FNA (GIP-Mediglobe), was used and FNA performed of this lymph node. Fine needle aspiration of the lymph node was performed, while continuous or intermittent suction was applied with a 10cc, 20cc and 30cc syringe. Aspiration was performed for 60 seconds for each technique. The slides were coded and then sent for cytopathologic examination. The pathologist was blinded to the technique used for FNA of the lymph node. The slides were examined and the results recorded independently by two pathologists who were blinded to each other's findings. Similar methodology was repeated in a 2 cm lymph node removed from another autopsy. Results: Pathologic examination of the first lymph node revealed metastatic transitional cell carcinoma of the bladder. The cellularity and quality of FNA with the 10 ml syringe was better than the 20 ml or 30 ml syringe. With the 10 ml syringe, continuous suction for one minute provided a better sample than intermittent suction. The second lymph node revealed metastatic non-small cell lung carcinoma. Although the FNA with a 20 ml or 30 ml syringe was diagnostic, the quality of the aspirate was not any better than FNA with a 10 ml syringe. Fine needle aspiration with a 20 ml or 30 ml syringe was more cumbersome, as it required more physical force. Conclusions: (1) Our study reveals that a 10 ml syringe for EUS guided FNA of mediastinal lymph nodes is adequate and a 20 ml or 30 ml syringe provides no additional advantage (2) Continuous rather than intermittent suction may provide a better cellularity during EUS guided FNA of lymph nodes.