Serous cystadenoma of the pancreas with papillary features: a diagnostic pitfall on fine-needle aspiration biopsy.

Serous cystadenoma of the pancreas is an uncommon neoplasm that occasionally exhibits papillary differentiation. The cytomorphologic structure of pancreatic serous cystadenoma has been rarely described, and, to our knowledge, such papillary morphologic structure has never been reported on fine-needle aspiration cytologic examination. We present a case of serous cystadenoma of the pancreas in a 77-year-old woman. Endoscopic ultrasonography showed a well-demarcated solid/cystic mass in the midbody of the pancreas, suggestive of solid pseudopapillary tumor. Aspiration cytologic examination, performed under endoscopic ultrasound guidance, showed a predominantly papillary epithelial neoplasm consistent with the radiologic impression. Gross and histologic examination of the excised specimen revealed a pancreatic serous cystadenoma with multifocal papillae. This case illustrates the cytomorphologic structure of serous cystadenoma that presents with prominent papillary differentiation on aspiration cytologic examination. The unusual cytologic appearance of this tumor introduces significant diagnostic challenges to the pathologist. Serous cystadenoma must be included in the differential diagnosis of pancreatic neoplasms with papillary morphologic structure as evaluated by fine-needle aspiration cytologic examination.