Ultrastructural characteristics of solid pseudopapillary tumors of the pancreas

We carried out an electron microscopic study of solid pseudopapillary tumors of the pancreas (operation material) from 15 patients. Two cell types were distinguished. Type 1 cells had large oval nuclei, little changed mitochondria, and short fragments of the granular cytoplasmic reticulum. These cells formed mainly pseudopapillary structures around the vessels. Type 2 cells were characterized by pronounced nuclear polymorphism with specific "coffee bean" picture. The cytoplasm of these cells contained many large mitochondria with clarified matrix and often destroyed cristae; lipofuchsin granules were seen. The ultrastructural characteristics of the solid pseudopapillary tumor cells attest to their epithelial origin.