Fine-needle aspiration of a pancreas with squamoid cyst of pancreatic duct and pancreatic duct stones: A case report of a rare pancreatic lesion and an unusual concurrent finding of stone-related crystals.

Squamoid cyst of pancreatic duct is a rare benign pancreatic lesion that is rarely encountered in fine-needle aspiration (FNA) and surgical resection specimens. Pancreatic stones can be seen in chronic pancreatitis, but stone-related crystals have previously not been described in pancreatic cytology. Presented here is a case report of a squamoid cyst of pancreatic duct with concurrent pancreatic duct stones. We describe the cytomorphology of this benign cyst, as well as the remarkable finding of polymorphous crystals on cyst fluid aspirate. We also describe the histology of the surgically resected cystic lesion. With the increase in detection of incidental pancreatic cysts on imaging, this case highlights the importance of awareness and recognition of benign non-neoplastic epithelial cysts on FNA sampling to avoid overtreatment. The presence of crystals on pancreatic FNA is an unusual finding, likely representing calcium carbonate crystals related to the formation of pancreatic duct stones.