Fig. 16

Gastrointestinal NET of the distal ileum with peritoneal dissemination in a 73-year-old woman, who had been complaining of diarrhea and symptoms of intestinal subocclusion for several months. a–c Axial CT images with intravenous contrast in the arterial phase show multiple hypervascular peritoneal implants of small size in the perihepatic space and the omental fat (red arrows). Axial (d, e) and coronal (f) CT images with intravenous contrast in the portal phase show an enhancing pseudonodular lesion in the distal ileum (yellow arrows), representing a primary NET. The tumor invades directly the adjacent mesentery, forming an enhancing soft tissue mass with punctate calcification (blue arrowhead). This mass retracts the mesenteric vessels, producing mild distension and mural thickening of the ileal loops in relation to chronic ischemic ileitis (green arrows). g, h H&E photomicrographs show a fibrous stroma with monomorphic cells that arrange in small groups and gland like structures, presenting fairly uniform nuclei, coarsely stippled chromatin ("salt and pepper") and finely granular cytoplasm, corresponding to a well-differentiated neuroendocrine tumor. i Immunohistochemistry shows positive staining for synaptophysin, confirming the neuroendocrine origin