Relevant infrastructural alterations in a pancreatic neuroendocrine tumor: an insulinoma case.

In this study, we focus our interest on some peculiar infrastructural abnormalities detected in an insulinoma case. Tumor pancreatic endocrine cells proliferated detrimental to exocrine counterpart, so that extensive areas of prevalent β-tumor cells can be seen. Two phenotypes of β-tumor cells can be identified: (1) β-tumor cells with full euchromatic and nucleolated nuclei and (2) β-tumor cells with heterochromatic and shrink nuclei. Because of stroma alteration, including basement membrane, cell-extracellular matrix junctions are also compromised. The mostly striking and important finding in this report for a case of insulinoma is the high fragility of plasma membrane of both two phenotypes of β-tumor cells. Cell-cell junctions, especially desmosomal junctions are severely altered, almost missing, plasma membranes showed shedding membrane vesicles and extensive dissolutions leading to pseudo-syncytia formation. Extravasated blood cells, including inflammatory cells contribute to the dramatic and extensive destructive areas of epithelial cells as well as stroma counterpart. Moreover, also the inner cell cytomembranes exhibit abnormalities: many β-tumor cells have excessive dilatations of nuclear envelope and endoplasmic reticulum. All above severe infrastructural abnormalities, especially down regulation of cell-cell and cell-extracellular matrix adhesions and plasma membranes fragility might result in aberrant cell behavior and, consequently, much care should be taken for the postoperatory patient evolution.