An Unusual Cytological Presentation of Solid Pseudopapillary Neoplasm of the Pancreas Mimicking Adenoid Cystic Carcinoma: a Case Report and Literature Review

Endoscopic ultrasound-guided fine-needle aspiration has become the common procedure for the diagnosis of pancreatic mass, and cytological examination is usually the first approach. Solid pseudopapillary neoplasm (SPN) cytologically represents papillary structures of branching capillaries surrounded by discohesive neoplastic cells. However, it may present various degrees of tissue degeneration, causing diagnostic challenges. Here, we report a 21-year-old female who had a 2-cm-sized mass in the pancreas head. Cytological examination revealed clumps of small round/oval cells that represented microcystic configurations with mucus, mimicking adenoid cystic carcinoma or mucinous adenocarcinoma. Cercariform cells, nuclear grooves/folding, and cytoplasmic vacuoles were not observed. Histopathological examination revealed confluent small glandular structures containing acidic mucus. The tumor cells were positively stained for β-catenin, CD10, and CD56, and negative for chromogranin A and E-cadherin, suggesting SPN, micropseudocystic variant. This variant has been scarcely described, but we should recognize it for accurate cytological triage of pancreatic tumors.