Neuroendocrine Tumors (NETs)

 

  • – NETs are heterogeneous group derived from neuroendocrine cells in many organs including GIT, Lung, adrenal gland (pheochromocytoma), thyroid (medullary carcinoma)
  • – Most NETs occur sporadically
  • – But a proportion are associated with genetic cancer syndromes
  •                 MEN-1
  •                 MEN-2
  •                 Neurofibromatosis type 1
  • – Gastroentero pancreatic NETs aeise in organs that are derived embryologically from the GIT
  • – Most GI NETs occur in small bowel
  • – The term ‘carcinoid’ is often used when referring to non-pancreatic gastroenteropancreatic NETs
  • – Nets may be benign (insulinoma, appendiceal carcinoid tumor) or malignant (small-cell carcinoma of the lung)
  • – Majority of gastroenteropancreatic NETs behave in an intermediate manner, with relatively slow growth but a propensity to invade and metastasise to remote organs, especially the liver

             Clinical features:

                       

                           Carcinoid syndrome:

  • – A classic feature of NET occur when vasoactive hormones reach the systemic circulation
  • – In the case of GI carcinoid      invariably means that the tumor has metastasized to the liver or peritoneum which allows secreted hormone to gain access to the systemic circulation. Hormones secreted by the primary tumor into the portal vein are metabolized and inactivated in the liver
  • – Clinical features of carcinoid syndrome
  •                   Episodic flushing, wheezing and diarrhoea
  •                   Facial telangiectasia
  •                   Cardiac involvement (TR, PS, right ventricular endocardial plaques) leading to heart failure

 

 

                    Pancreatic Neuro-endocrine Tumors:

 

                                                  Investigations:

  • – 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin to confirm diagnosis
  • Imagings:
    Ultrasound, CT, MRI and/or radio-labelled somatostatin analogue to identify the primary tumour and staging
  • Biopsy of the primary tumour or a metastatic deposit to confirm the histological type
  • Immunohistochemical staining for the proteins chromogranin A and synaptophysin

 

                               Treatment:

  • –  Solitary tumours         Surgical resection
    For metastatic or multifocal primary disease surgery is usually not indicated, unless there is a complication such as gastrointestinal obstruction
  • Diazoxide    ⇒  reduce insulin secretion in insulinomas
  • High doses of PPI  ⇒   suppress acid production in gastrinomas
  • Somatostatin analogues to reduce the symptoms of carcinoid syndrome and of excess VIP production
  • Chemotherapy and radiotherapy, have limited efficacy

 


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