Impact of Needle Size on Pancreatic FNA Cytology

Abstract

INTRODUCTION: 22-gauge needles are typically used for most pancreatic mass endoscopic ultrasound-guided fine-needle aspiration (EUS/FNA) procedures. It is unknown whether a larger or smaller gauge needle may actually provide better diagnostic material. 19-gauge needles may provide more diagnostic material but with more blood, while 25-gauge needles may provide less bloody samples but with less diagnostic material. The purpose of this preliminary study was to determine if there is a difference in cytologic yield, diagnostic material and background blood using various needle sizes for pancreatic FNA, and to determine whether an autopsy model could be used to test diagnostic yields for EUS/FNA. METHODS: The pancreas was removed during autopsies, which were performed within 24 hours of death. FNA was immediately performed upon removal using 1.5-inch long 19-, 22-, and 25-gauge needles attached to a 10cc aspiration syringe using negative pressure. Three passes were made with each needle. Aspirate smears were air-dried, alcohol-fixed, and stained with Diff-Quik and H&E stain, respectively. A single pathologist, blinded to the needle size used, evaluated each pass for cellularity and blood (1=low, 2=moderate, 3=high), and the presence of ductal cells, acinar cells and diagnostic material (yes/no), as defined by having an adequate number of cells for interpretation. RESULTS: Eleven pancreatic autopsy specimens were aspirated. Mean age of the patients was 51 years (range 38-77). None of the patients had known prior pancreatic disease. Results are shown below for the 24 passes obtained with each needle size. Diagnostic material was obtained from at least one pass for each needle size in all patients using the 25-guage needle, and in 7 of 8 using a 22- or a 19-gauge needles. CONCLUSIONS: 1) 19-, 22-, or 25-gauge needles for pancreatic FNA all provided adequate diagnostic material, with similar cellularity and background blood. 2) The use of an autopsy model for pancreatic FNA may be an effective means for comparing diagnostic yield using different EUS/FNA needles. 3) Larger needle size for EUS guided FNA of the pancreas may not improve diagnostic yield. Further research is needed to determine if needle size impacts cytologic yield in pancreatic malignancy and fibrosis.