These form part of a spectrum with the pancreatic neuroendocrine tumours, and may be referred to as gastro-enteral pancreatic neuroendocrine tumours (GEP-NETs). In general, neuroendocrine tumours of the pancreas do more interesting things (eg. insulinoma, gastrinoma) whereas those of the gastrointestinal tract are referred to as carcinoid tumours and may produce the carcinoid syndrome.
Most tumours arise from the small bowel (40%); a significant number from the appendix (25%) and large bowel (25%); a smaller number arise from the stomach and duodenum (< 10%); and rarely from the oesophagus. They can occur at any age but are most common in later life.
Aetiology and Pathogenesis
Individual causative factors
Modes of spread
Macroscopic appearance is of a well demarcated, small, yellow-tan, firm nodule.
Neuroendocrine tumours typically display a variety of neuroendocrine architectural patterns, including trabeculae, nests, strands or sheets. The cells are relatively bland cytologically with pink, granular cytoplasm and a salt and pepper nucleus. Some tumours may show some anaplastic features (eg. necrosis, mitoses) and are often classified as moderately differentiated neuroendocrine tumours.
Cells stain positively for synaptophysin and chromogranin.
Staging / Classification
TNM or other staging system if relevant