Solid pseudopapillary neoplasm of the pancreas: a case report with review of the diagnostic dilemmas and tumor behavior

Abstract

Solid pseudopapillary neoplasm of the pancreas is a rare tumor of the pancreas often detected initially on imaging. Of uncertain histogenesis, it has a low-grade malignant potential with excellent post-surgical curative rates and rare metastasis. Despite advances in imaging, pseudocysts and other cystic neoplasms feature in the differential diagnosis. Pathological and/or cytological evaluation remains the gold standard in reaching a definitive diagnosis. On morphology alone, other primary pancreatic tumors and metastatic tumors pose a diagnostic challenge. Recent advances in immunohistochemical characterization have made the histopathologic diagnosis more specific and, in turn, shed light on the likely histogenesis of this rare tumor. We report a case of solid pseudopapillary neoplasm of the pancreas that was suspected on radiology and diagnosed intraoperatively on imprint cytology guiding definitive surgery. The diagnostic dilemmas are reviewed.

Keywords: Beta-catenin; E-cadherin; Pancreas; Solid pseudopapillary neoplasm (SPN).

Figure 1

CT scan abdomen and pelvis shows an enhancing, rounded, well defined, cystic (C) and solid (S) tumor located in proximity to the spleen; (1A) and supero-anterior to the left kidney; (1B) (arrowheads).

Figure 2

Solid pseudopapillary neoplasm (SPN) of the pancreas; macroscopic and microscopic appearance. (A) globular encapsulated tumor with solid brown areas and a whitish nodule; (B) Intraoperative imprint cytology shows the pseudopapillary arrangement of uniform cells around arborising vessels (Diff Quik × 40); (C) The tumor forms pseudorosettes and pseudopapillae projecting into cystic spaces (H&E × 40); (D)Tumor cells are polygonal with eosinophilic cytoplasm, vesicular nuclei with grooves with minimal atypia and occasional mitosis (arrow) (H&E × 400).

Figure 3

Immunophenotypic features of SPN. (A) Strong nuclear positivity for ß-catenin (DAB × 400); (B) The surrounding pancreatic tissue expressing e-cadherin (arrows) while the tumor is negative (arrowhead), (DAB × 40); (C) Diffuse nuclear progesterone receptor (PR) positivity in the tumor cells (IHC with DAB ×100); (D) Weak, focal, granular cytoplasmic positivity for chromogranin in the tumor cells (DAB × 400).