Heparin priming of EUS-FNA needles does not adversely affect tissue cytology or immunohistochemical staining

Background and study aims  Endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) or biopsy (FNB) is an indispensable diagnostic tool. Improvements in needling technique have led to increasing tissue yields. Blood clogging of the needle can cause difficulties with specimen handling and stylet passage, which improves when the needle is primed with heparin before use. However, the effect of heparin on cytology, histology or immunochemistry (IHC) of FNA and FNB specimens is unknown. The goal of the study was to evaluate heparin priming on cytologic/histologic appearance, IHC staining, ease of stylet passage, and specimen bloodiness. Patients and methods  This was a retrospective study of patients undergoing EUS-FNA/FNB. Needle sizes were 25 gauge (g), 22 g, and 19 g. Heparin priming of the needle was done and the stylet replaced ("dry heparin") or suction attached without replacing the stylet ("wet heparin"). Smears and cellblocks were examined by pathologists, and IHC staining were done as needed. Specimen bloodiness was compared with matched controls. Results  Adequate tissue yields were obtained in all samples (37 heparin, 36 no heparin). Heparin priming did not exhibit negative effects on cytologic or histologic interpretation of the specimens, nor IHC. There was no difference in cellblock bloodiness between the heparin primed needle specimens and the non-heparin control group. . Conclusions  Heparin priming of EUS-FNA or FNB needles does not negatively affect cytologic or histologic interpretation, nor interfere with IHC. In addition, heparin priming does not increase specimen bloodiness. When the "wet suction" technique is used for EUS-FNA, heparin priming can be used instead of saline priming of the EUS needle.