EUS-FNA diagnosis of pancreatic tophaceous gout: Two rare cases.

We report two patients with pancreatic tophaceous gout diagnosed by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) of presumed cystic mass lesions. The first case involved a patient who had a recent episode of acute pancreatitis 6 months prior, with subsequent imaging concerning for a pseudocyst or mass lesion. The second case involved a patient with epigastric pain associated with a pancreatic head cystic mass and an erroneous original diagnosis of a mucinous pancreatic neoplasm on EUS-FNA. Diff-Quik stained direct smears on fresh material obtained from EUS-FNA of the lesions showed chalky debris with needle shaped negatively birefringent crystals consistent with gout. For the first case, the chalky material was not present on the H&E stained paraffin embedded formalin fixed cellblock slides. The importance of inclusion of cytologic specimen preparations to examine monosodium urate crystals is emphasized.