Serous Cystadenoma of the Pancreas: Limitations and Pitfalls of EUS Guided Fine Needle Aspiration Biopsy

Abstract

BACKGROUND: Expectant management of serous cystadenoma (SCA) of the pancreas requires an accurate preoperative diagnosis. Previously published cytologic diagnostic sensitivities have ranged widely, from 10% to 100%. In the current study, the authors evaluated the diagnostic sensitivity of endoscopic ultrasound (EUS)-guided fine-needle aspiration biopsy (FNAB) and cross-sectional imaging for SCA. METHODS: Group I consisted of 21 histologically confirmed SCAs. Group II (n = 7 lesions) lacked histologic confirmation and was defined by EUS findings that were consistent with SCA and a cyst fluid carcinoembryonic antigen (CEA) level <5 ng/mL. Group III was comprised of 2 nonserous and potentially malignant cysts of the pancreas for which a preoperative diagnosis of SCA was considered. Cross-sectional imaging data were recorded. The smears were evaluated for the presence of serous lining epithelium, gastrointestinal-contaminating epithelium, and inflammatory cells including hemosiderin-laden macrophages. The authors also evaluated the presence of hemosiderin-laden macrophages in a series of 110 FNA specimens from histologically confirmed neoplastic mucinous cysts of the pancreas and 45 pseudocysts of the pancreas. RESULTS: Prospectively among Group I lesions, the appearance on computed tomography (CT) was considered definitive for SCA in 3 of 12 cases (25%). The histologically confirmed SCA cases had CEA levels of <5 ng/mL, except for 1 case for which the CEA level was 176.5 ng/mL. A cytologic diagnosis of SCA was made prospectively in only 1 CT-guided case. Retrospectively, 3 intraoperative FNAs and 1 additional CT-guided aspirate contained rare epithelial cells of a SCA. None of the EUS-guided aspirates demonstrated serous epithelium. Among Group II aspiration specimens, only 1 contained serous epithelial cells. Approximately 52% of the EUS-guided aspirates demonstrated gastrointestinal contamination. This glandular epithelium was categorized as atypical in 2 cases. Hemosiderin-laden macrophages were identified in 43% of the SCAs. Conversely, only 2% of neoplastic mucinous cysts and 9% of pseudocysts produced hemosiderin-laden macrophages in aspirate fluid. CONCLUSIONS: In the current study, serous epithelial cells were identified in <20% of cases. Gastrointestinal-contaminating epithelium, often observed in EUS-guided aspirates, further contributes to difficulties in interpretation. The presence of hemosiderin-laden macrophages as a surrogate marker for SCA requires further study. A preoperative diagnosis of SCA remains a challenge, and an EUS-guided FNAB is unlikely to provide the high level of diagnostic accuracy necessary to permit a nonoperative approach.