Primary malignant solid pseudopapillary tumors of the gastroduodenal area.

Extrapancreatic cases of solid-pseudopapillary tumor (SPT) are exceedingly rare. We report here two cases of primary tumors located in the gastroduodenal region, morphologically identical to pancreatic SPT, but particular by their immunohistochemical features and malignant evolution. Clinical charts and all available histopathological material were reviewed; complementary immunohistochemical investigations and molecular analyses were performed. The patients were a 32-year-old female, submitted to surgical resection for a tumor of the prepyloric region, and a 73-year-old male presenting with a duodenal tumor and synchronous liver metastases. In the two cases, the primary tumor and all the metastases available for study were morphologically indistinguishable from typical pancreatic SPT. However, their immunohistochemical profile was characterized by the absence of hormone receptor expression and of nuclear localization of beta-catenin and E-cadherin. In the only case in which it was feasible, molecular analysis did not identify any mutation in the CTNNB1 gene. Both tumors had a malignant behavior, with extensive metastatic dissemination. In conclusion, we report two unusual cases of extrapancreatic SPT arising in the gastroduodenal area, associated with a malignant course and an extensive metastatic dissemination.