EUS for Pancreas Cysts: What Should We Be Sampling?

The growing resolution and more frequent use of imagingmethods has increasingly identiﬁed pancreatic cysts,ranging from benign serous and pseudocysts to premalig-nant or malignant mucinous cystic neoplasm (MCN). Dueto the disparate course and management of benign cystsversus cystic neoplasms or pre-neoplasms, unambiguouslesion identiﬁcation is essential, which is not always pos-sible with conventional cross-sectional imaging [1]. Thus,an increasing number of centers are utilizing endoscopicultrasound (EUS) for further characterization of pancreaticcysts with high resolution images of cyst morphology, size,presence and type of septations, presence of solid compo-nents, and the ability to sample cyst contents using ﬁneneedle aspiration (FNA) and to perform biopsies. Charac-teristics such as diameter[3 cm and the presence of muralnodules may be the best predictors of malignant transfor-mation of MCN or side-branch type intraductal papillaryneoplasms (SB-IPMN) [2]. In some cases, however, biopsyof solid material or aspiration of cyst ﬂuid is essential toconﬁrm the diagnosis. Thus, when a pancreas cyst isdetected on CT or MRI, the clinical question often arises asto whether EUS should be performed and, furthermore, ifadditional FNA or biopsy is helpful.In this month’s issue of Digestive Diseases and Sci-ences, Lim et al. [3] report their ﬁndings in ‘‘Factorsdetermining diagnostic yield of EUS guided ﬁne-needleaspiration for pancreatic cystic lesions: a multicenter Asianstudy.’’ The authors include a multicenter analysis of 298patients with diverse pancreatic cystic lesions who under-went EUS of whom 132 (44 %) underwent EUS–FNA.FNA cytology with a single pass was only 29 % when solidcomponents are not present. Furthermore, their studydemonstrated a higher yield (44 %) when solid componentswere biopsied during a single pass, which increased to78 % with multiple passes. Although biochemical markerssuch as carcinogenic embryonic antigen (CEA) and amy-lase measured in cyst ﬂuid aspirates are frequently used toaid in diagnosis of pancreatic cysts, the authors focused oncytologic yield from EUS–FNA. In the literature, theoverall yield of EUS–FNA for cytologic analysis of inde-terminate pancreatic cystic lesions is 31–37 % [2, 4].Morphologic features noted by high resolution EUSimages of small pancreatic cysts can help differentiatemucinous-type cysts from others. Nevertheless, in a recentstudy, expert endosonographers were evaluated for theirability to make a diagnosis of pancreatic MCN based onEUS appearance alone without FNA. The accuracy wasonly 23–46 % despite the use septations, mural nodules,solid components, and communication with the pancreaticduct as criteria [5]. Therefore, FNA for ﬂuid analysis orbiopsy of solid materials may add to diagnostic yield,particularly for indeterminate cysts. Solid material within acyst may represent debris but could also arise frommalignancy.Several studies have addressed the acquisition of pan-creatic cyst specimens and types of analysis that providethe highest diagnostic yield. Cytologic analysis of aspiratedﬂuid is usually of low yield due to the unlikelihood thatpancreatic cysts shed adequate cells for evaluation.Accordingly, a recent study demonstrated that FNA of thecyst wall rather than ﬂuid aspiration alone can improvediagnostic yield up to 81 %, with the majority of casesdemonstrating mucinous epithelium [6]. Other investiga-tors have examined the use of a cytology brush passedthrough a 19-gauge FNA needle to gather more cellular