Clinicopathological Analysis of Solid Pseudopapillary Tumor (SPT) of the Pancreas

ABSTRACT

PURPOSE: Solid pseudopapillary tumor (SPT) of the pancreas is a rare benign or low-grade pancreatic neoplasm with distinct clinicopathologic features. The purpose of this study was to evaluate the clinical presentation of SPT and to examine the etiology of this tumor by performing immunohistochemical staining. METHODS: From October 1994 to March 2005, 35 cases of SPT who underwent operations were retrospectively reviewed. The clinicopathologic findings and late results of treatment were studied in 7 cases of borderline malignant SPT and in 28 cases of the benign SPT. Immunohistochemical staining was performed for alpha1-antitrypsin, alpha1-antichymotrypsin, neuron specific enolase, chromogranin, synaptophysin, vimentin and cytokeratin. RESULTS: The mean age of the patients was 31.8 years. SPT's were more common in women (77.1%) and the tumors were usually located in the body and the tail of the pancreas (68.6%). There were statistically significant differences in the men (P=0.016), for the masses with calcification (P=0.029), and for the solid masses (P=0.018) between the malignant SPT (including the borderline malignant SPT) and the benign SPT (P=0.014). The SPTs stained positive for alpha1-antitrypsin, neuron specific enolase, and vimentin in all cases, and they were alpha1-antichymotrypsin positive in 94.1% (16/17), chromogranin positive in 18.8% (3/16), synaptophysin positive in 12.5% (2/16), and cytokeratin positive in 18.2% (2/11). All 35 patients underwent curative resection and they are all alive without any evidence of recurrence at a mean follow-up of 44.2 months. CONCLUSION: SPT is a rare tumor that behaves less aggressively than other pancreatic tumors, and surgical resection can result in cure. This tumor thought to originate from a stem cell capable of differentiating into endocrine cells or exocrine cells.