NETs are tumours arising from cells of neuroendocrine origin. They can be classified into non-functioning tumours or functioning tumours which cause symptoms due to peptide and hormone release.
The majority of NETs arise in the GI tract or pancreas
All GI NETs can present with non-specific symptoms such as vague abdominal pain, nausea and vomiting and abdominal distension
Carcinoid syndrome occurs following metastasis of a carcinoid tumour whereby the metastasised cells begin to oversecrete bioactive mediators, such as serotonin, prostaglandins, and gastrin, into the circulation.
Chromogranin A (CgA) should be tested for all patients, as it is the only general marker for NETs that is found in high concentrations regardless of whether the tumour is functional or non-functional.
Urinary 5-hydroxyindoleacetic acid is a breakdown product of serotonin
