EUS for Pancreas Cysts: What Should We Be Sampling?

Abstract

The growing resolution and more frequent use of imaging methods has increasingly identified pancreatic cysts, ranging from benign serous and pseudocysts to premalignant or malignant mucinous cystic neoplasm (MCN). Due to the disparate course and management of benign cysts versus cystic neoplasms or pre-neoplasms, unambiguous lesion identification is essential, which is not always possible with conventional cross-sectional imaging [1]. Thus, an increasing number of centers are utilizing endoscopic ultrasound (EUS) for further characterization of pancreatic cysts with high resolution images of cyst morphology, size, presence and type of septations, presence of solid components, and the ability to sample cyst contents using fine needle aspiration (FNA) and to perform biopsies. Characteristics such as diameter [3 cm and the presence of mural nodules may be the best predictors of malignant transformation of MCN or side-branch type intraductal papillary neoplasms (SB-IPMN) [2]. In some cases, however, biopsy of solid material or aspiration of cyst fluid is essential to confirm the diagnosis. Thus, when a pancreas cyst is detected on CT or MRI, the clinical question often arises as to whether EUS should be performed and, furthermore, if additional FNA or biopsy is helpful.In this month's issue of Digestive Diseases and Sciences, Lim et al. [3] report their findings in ''Factors determining diagnostic yield of EUS guided fine-needle aspiration for pancreatic cystic lesions: a multicenter Asian study.'' The authors include a multicenter analysis of 298 patients with diverse pancreatic cystic lesions who underwent EUS of whom 132 (44 %) underwent EUS-FNA.FNA cytology with a single pass was only 29 % when solid components are not present. Furthermore, their study demonstrated a higher yield (44 %) when solid components were biopsied during a single pass, which increased to 78 % with multiple passes. Although biochemical markers such as carcinogenic embryonic antigen (CEA) and amylase measured in cyst fluid aspirates are frequently used to aid in diagnosis of pancreatic cysts, the authors focused on cytologic yield from EUS-FNA. In the literature, the overall yield of EUS-FNA for cytologic analysis of indeterminate pancreatic cystic lesions is 31-37 % [2,4].Morphologic features noted by high resolution EUS images of small pancreatic cysts can help differentiate mucinous-type cysts from others. Nevertheless, in a recent study, expert endosonographers were evaluated for their ability to make a diagnosis of pancreatic MCN based on EUS appearance alone without FNA. The accuracy was only 23-46 % despite the use septations, mural nodules, solid components, and communication with the pancreatic duct as criteria [5]. Therefore, FNA for fluid analysis or biopsy of solid materials may add to diagnostic yield, particularly for indeterminate cysts. Solid material within a cyst may represent debris but could also arise from malignancy.Several studies have addressed the acquisition of pancreatic cyst specimens and types of analysis that ...