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.
Epidemiology
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
Pathogenesis
Natural History
Precursor lesions
Modes of spread
Clinical Presentation
Symptoms
Signs
Blood Findings
Imaging Findings
Tumour Features
Macroscopy
Macroscopic appearance is of a well demarcated, small, yellow-tan, firm nodule.
Microscopy
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.
Immunohistochemistry
Cells stain positively for synaptophysin and chromogranin.
Genetics
Staging / Classification
TNM or other staging system if relevant