Endoscopic Ultrasound―Guided Fine Needle Aspiration Cytology Diagnosis of Solid Pseudopapillary Tumor of the Pancreas: A Report of 3 Cases

Solid pseudopapillary tumor of the pancreas (SPTP) is an exceedingly rare pancreatic tumor. We present the clinical, endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) cytologic features and immunohistochemical findings performed on cell blocks of 3 SPTPs. Three females (17-32 years old) were admitted to our hospital due to unexplained episodic abdominal pain. EUS confirmed the presence of a mass in the body and tail of the pancreas (2 cases) and in the head (1 case), with distinct borders and occassional dilation of the peripheral part of the pancreatic duct. EUS-FNA cytology specimens consisted of single cells and aggregates of uniform polyhedral cells, forming branching papillary clusters with delicate fibrovascular cores and nuclear overlapping (2 cases) and glandlike structures (1 case). Variable hyaline, myxoid stromal elements and naked capillaries were also seen. The cells had bland nuclear features, small nucleoli, nuclear grooves in some of them and focally cytoplasmic projections. Mitoses and necrosis were not observed. The immunohistochemistry on cell blocks revealed: vimentin+ (3 cases), CA19.9+ (2 cases), cytokeratin 7+ (focal, intensive, 1 case), synaptophysin+ (1 case), MUC1+ (focal, intensive, 1 case), EMA+ (diffuse weak, 1 case), a1-antitrypsin and a1-antichymotrypsin+ (focal intensive, 2 cases), progesterone+ (1 case), chromogranin-A- (3 cases) and NSE- (3 cases). Cytologic and immunohistochemical findings were strongly suggestive of SPTP. Surgical resection confirmed the diagnosis in all cases. EUS-FNA cytology features and immunohistochemistry provide the diagnosis of SPTP with accuracy.