Solid-pseudopapillary tumor

This rare tumor usually occurs in women in their second or third decades of life. It presents as a large abdominal mass and has low malignant potential, although rare cases of metastatic disease have been reported. Histologically, it is characterized by fine fibrovascular septa forming the core of pseudopapillary structures, which result from ischemic degeneration and fragmentation of solid tumor areas. The epithelial cells cling to the septa, creating the appearance of papillary structures.

Cytologic diagnostic features

High cellularity
Loosely cohesive groups and single cells
Branching fibrovascular structures lined by tumor cells
Delicate granular cytoplasm, indistinct cell borders
Benign nuclear features
Nuclear grooves
Background of blood, foamy cells, necrotic debris

Immunohistochemical studies demonstrate vimentin positivity, whereas the tumor cells are negative for cytokeratins, pancreatic enzymes and neuroendocrine markers. The differential diagnosis includes cystic neoplasms, ductal adenocarcinoma, acinar cell carcinoma and endocrine tumors.