What are the Neuroendocrine Tumours of the Gastroenteropancreatic System (GEP-NET) and how common are they?

Neuroendocrine tumours (NETs) of the digestive system originate from the neuroendocrine cells of the gastrointestinal tract and pancreas, with an incidence of 3.56 per 100,000 in the general population. The majority are well-differentiated, slow-growing tumours, with the minority showing aggressive behaviour.


At what age do neuroendocrine tumours of the gastroenteropancreatic system (GEP-NET) occur?

They can occur at any age, but usually appear between the fourth and sixth decade.


How do neuroendocrine tumours (NETs) of the digestive system present?

NETs of the digestive system usually develop as:

  • Sporadic tumours, but may be related to the
  • hereditary genetic endocrine tumour syndromes
  • The majority of them are non-functional and the symptoms they give are mainly due to local compression or metastatic disease, such as:
  • atypical abdominal pain

However, these tumours may secrete active substances/hormones, leading to separate clinical syndromes.


What are the Islet Cell tumours?

Functional neuroendocrine tumours of the pancreas, i.e. tumours that originate from the islets of Langerhans and produce hormones, are also called islet cell tumours and are classified into the following types:


How are neuroendocrine tumours (NETs) of the digestive system diagnosed?

A significant number of these tumours are diagnosed incidentally on imaging tests performed for another disease.

The diagnosis of gastrointestinal NETs is made by:

  • cytology and confirmed by:
  • biopsy, while the localisation of the tumour and the extent/staging of the disease is determined by imaging studies, such as:
  • CT and MRI,
  • Somatostatin receptors scintigraphy (octreoscan) and
  • endoscopic ultrasound.

Their secretory capacity is determined by:

  • measurement of the active substances excreted in the blood and urine.

Similarly, the diagnosis of pancreatic NETs is made by:

  • measurement of the hormone they secrete in excess and the localization of the tumour is done by:
  • imaging modalities, while sometimes invasive diagnostic tests are required, such as:
  • selective arterial calcium stimulation test

How are neuroendocrine tumours (NETs) of the digestive system treated?

The treatment of choice for NETs is:

  • their radical excision.

In case of metastatic disease:

  • surgical removal must be combined with other treatments, such as:
  • chemoembolization for liver metastases,
  • treatment with peptide receptor radionuclide and
  • the targeted molecular therapies
  • Somatostatin analogs have both anti-secretory and anti-tumoral effects.

Regular monitoring is important for early diagnosis of possible relapses and includes blood and imaging tests at intervals determined by the stage of the disease.