Solid pseudo-papillary tumor of the pancreas: Diagnosis by endoscopic ultrasound-guided fine needle aspiration cytology and immunocytochemistry.

Pseudopapillary tumor (SPT) is a rare primary pancreatic neoplasm of uncertain origin and low malignant potential that typically affects young females, mostly in their third decade of life. There are only a few reports on fine needle aspiration (FNA) cytology diagnosis of this neoplasm. We report one such case which was diagnosed based on cytomorphologic and immunocytochemical features on endoscopic ultrasound (EUS) guided FNA smears. A 24-year-old woman presented to the gastroenterology clinic with 3-month history of epigastric pain, anorexia, and weight loss (10 kg over same time period). Abdominal CT revealed a large (13X11 cm) heterogeneous cystic lesion occupying most of the pancreatic body. EUS examination confirmed the presence of a large mixed cystic-solid lesion occupying most of the pancreatic body and neck. EUS-guided FNA smears showed tumor cells in sheets with papillary/pseudo-papillary and acinar formation. The tumor cells had abundant clear and vacuolated cytoplasm and round to oval nuclei with bland chromatin. PAS staining revealed positively stained capillary networks at the core of the papillary/pseudo-papillary structures. In addition, there were PAS positive intra-cytoplasmic and extra-cellular globules which were diastase resistant. Immuno-cytochemical staining on direct smears revealed positive reaction for cyclinD1, vimentin, CD56, beta-catenin, CD10 and progesterone receptor. Thus, this is the example of an extremely rare neoplasm which had a typical clinical and imaging setting, and could be conclusively diagnosed because of characteristic cytomorphological and immunocytochemical features.