Solid-pseudopapillary tumor of the pancreas: a typically cystic carcinoma of low malignant potential.

Solid-pseudopapillary tumors are uncommon neoplasms of low malignant potential generally occurring in young women. They often cause few symptoms and may reach a large size by the time they are detected. Degenerative cystic changes are common, and the clinical presentation is often that of a cystic pancreatic tumor. Pathological features include solid, cellular, hypervascular regions without gland formation, and degenerative pseudopapillae. The cells contain eosinophilic granules rich in alpha-1-antitrypsin and the nuclei are typically grooved. Despite its characteristic microscopic appearance, the immunophenotype (positive for vimentin, alpha-1-antitrypsin, and neuron specific enolase) is not specific and does not define a line of differentiation corresponding to any normal pancreatic cell type. Ultrastructural studies have also failed to identify specific differentiated features. Nonetheless, the biological behavior of solid-pseudopapillary tumor is well established. The tumor is indolent, with infrequent metastases to liver or peritoneum and usually long survival, even in the presence of disseminated disease.