Extrapancreatic solid pseudopapillary neoplasm: Report of a case of primary retroperitoneal origin and review of the literature.

Solid pseudopapillary tumors (SPTs) occurring as primary tumors outside the pancreas are exceedingly rare. The present study reports such a case occurring as a non-functional adrenal tumor in a 22-year-old female. The tumor was completely removed from the retroperitoneum by laparoscopic surgery. A well-defined, encapsulated tumor measuring 6×6×5 cm was histologically characterized by a combination of the solid and pseudopapillary growth patterns of tumor cells with eosinophilic cytoplasm. Ectopic pancreatic tissue was also found histologically within the resected tumor. On immunostaining, the tumor was positive for progesterone receptor, CD56, cytokeratin and CD10. The morphological and immunohistochemical features were compatible with those of SPT. To the best of our knowledge, this is the first case report of extrapancreatic SPT with evidence of a pre-existing ectopic pancreas in the retroperitoneum. A review of the published English literature uncovered 12 cases of extrapancreatic SPTs, and revealed that extrapancreatic SPTs are likely to have a favorable clinical course and a clinical profile similar to their pancreatic counterparts.