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The PSC published guidelines for sampling of pancreatobiliary lesions. This section will focus only on FNA of pancreatic masses. ERCP-guided brush cytology of the pancreatic duct can be performed for sampling of the main pancreatic duct in which a wire-guided brush is used to collect cells from a strictured pancreatic duct.

A number of imaging modalities may be used to guide pancreatic FNA, including US, EUS, and CT scans. EUS FNA is now the procedure of choice in establishing the diagnosis of a pancreatic lesion. Linear endosonographic instruments are required to target lesions for FNA [37]. Simple aspiration needles (usually 22- or 25-G) are used for the procedure. Both caliber needles yield the same cytologic material [38]. Smaller 25-G needles are preferable for sampling suspected PDAC as they are easier to use. They are also preferred for vascular lesions and aspiration of lymph nodes. Core biopsy and Tru-Cut needles are used for lesions such as stromal cell tumors, panNETs, and tumors with a suboptimal cytology yield and lesions suspicious for autoimmune pancreatitis. The EUS-FNA procedure can be difficult to perform due to vessel interposition, duodenal stenosis, bleeding, and tumor firmness. Prior gastric surgery or bypass will limit accessibility of the device to the pancreas. A 22-G beveled needle called Procore (Echo Tip) is available for use with the EUS device that produces a core-like tissue fragment.

Mucinous cysts are aspirated using a 22-G needle due to the high viscosity of the cyst fluid. Serous cystadenomas and cystic NETs should be aspirated with a 25-G needle as the cyst fluid is not viscous. Pseudocysts should be aspirated with a 22- or 19-G needle in order to evacuate the entire lesion, which may become contaminated by FNA. Mural nodules and any adjacent masses can be aspirated after the cyst fluid is aspirated. The cyst fluid is centrifuged and may be sent for CEA and DNA mutational analysis.