Diagnosis of an aneurysm masquerading as a pancreatic-cyst lesion at EUS

Background: EUS-guided FNA is commonly performed for evaluating pancreatic-cyst lesions. However, not all such lesions are true cystic neoplasms of the pancreas. Objective: Determine the frequency at which aneurysms mimicking cysts are encountered during EUS evaluation of the pancreas. Study Design: Observational study. Setting: Tertiary referral center. Patients: Consecutive patients found to have pancreatic cyst lesions at EUS. Interventions: Patients with a cyst lesion in the pancreas that was suspicious for an aneurysm at EUS underwent abdominal CT imaging for a definitive diagnosis. Main Outcome Measures: To determine the frequency at which aneurysms are encountered during EUS while evaluating pancreatic-cyst lesions and to describe the EUS characteristics of an underlying aneurysm. Results: Four of 413 lesions (0-97%, 95% confidence interval 0.26%-2.5%) that appeared as pancreatic cysts at EUS were diagnosed to be aneurysms: 2 were splenic artery aneurysms, I was an aneurysm of the gastroduodenal artery, and another was an infrarenal aortic aneurysm. The aneurysms had a characteristic donut-like appearance at EUS: a thick outer wall with a central anechoic area. Limitations: Observational study; small sample size. Conclusions: Aneurysms can masquerade as pancreatic-cystic lesions. Awareness of this entity is important because an inadvertent FNA during EUS may potentially lead to serious complications.