Endoscopic ultrasound guided fine-needle aspiration of lymph nodes and solid masses: factors influencing the cellularity and adequacy of the aspirate.

Goals: To study the factors that influence the cellularity and adequacy of endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA).

Background: An on-site cytopathology service is preferred during EUS-guided FNA. However, this is not always available. Factors that influence the aspirate cellularity and adequacy have not been well defined in the absence of on-site cytopathology.

Study: EUS-guided FNA procedures without an on-site cytopathologist from a single center were retrospectively studied. FNA of solid masses and lymph nodes (LN) were included. The FNA cellularity, hemorrhagic content, and endoscopists' assessment of adequacy were analyzed.

Results: A total of 166 patients from January 2009 to October 2010 were included. A total of 520 FNA passes were performed. Of the 166 lesions, 70 (42.2%) were solid masses and 96 (57.8%) were LNs. A 22-G needle was used in 72.3% and 25 G in 27.7% of the patients. The median (range) number of FNA passes was 3 (1 to 7) for LNs and 3 (1 to 5) for solid masses. With this, the endoscopists had an accuracy of 92.2% (153/166) for obtaining an adequate aspirate. Of the 166 samples, 4 (2.4%) were acellular, 20 (12.0%) sparsely cellular, 52 (31.4%) moderately cellular, and 90 (54.2%) highly cellular. The 25-G needle had significantly more adequate aspirates than the 22-G needle for solid masses (P=0.011). Also, increasing passes correlated with higher cellularity (P=0.002) and an adequate aspirate (P=0.021). No correlation was found for LN FNA. Lesion size did not influence the cellularity or adequacy (P>0.05). The degree of hemorrhage was not influenced by the needle gauge, number of passes, or lesion size. The diagnostic yield was not affected by hemorrhage in the sample (P>0.05).

Conclusions: EUS-guided FNA obtains a high proportion of adequate aspirates for LNs and solid masses, even without an on-site cytopathologist. Small proportions of inadequate samples still occur. For solid masses, a 25-G needle with at least 3 passes is more likely to provide an adequate aspirate than a 22-G needle and fewer passes. Hemorrhage did not affect the cytopathology's ability to make a diagnosis.