• The disease
• Diagnosis
• Treatment options

Definition

Endocrine cells are found throughout the body and can cause neuroendocrine tumors (NET) in many organs. In approximately 60% of cases, NETs appear in the digestive system (GI-NETs). They can be located all along the digestive tract, from the oesophagus to the rectum, in the colon and the pancreas. These primary tumors can then spread to other organs, especially the liver.
They are called neuroendocrine tumors, because the tumor cells in NETs share certain characteristics with nerve cells and endocrine cells, such as the ability to secrete hormones.

Symptoms and impact on health

Many neuroendocrine tumors are not associated with any clinical symptoms, either because they are small or because they do not secrete hormones. When they are symptomatic, symptoms vary depending on the organ affected and develop slowly over several years.

Symptoms caused by tumor growth
Although made up of endocrine cells initially, the majority of gastrointestinal NETs do not cause hyper-secretion of hormones and therefore patients display no clinical symptoms. These so-called non-functional tumors are not found until they grow larger and produce a range of different symptoms:

• abdominal pain or discomfort,
• bloating,
• constipation,
• intestinal occlusion,
• presence of blood in stools,
• nausea or vomiting,
• weight loss,
• jaundice.

Symptoms caused by secretion of hormones by the tumor
Some GI-NETs secrete excessive hormones, which cause a number of different conditions:

• diarrhea
• weight loss,
• dehydration,
• redness of the skin and hot flushes,
• wheezing,
• palpitations.

Risk factors

There are no identifiable risk factors for the majority of patients with neuroendocrine tumors. In rare cases, gastrointestinal NETs may form part of a hereditary disease, in which case we refer to tumor predisposition syndrome and a possible association with other tumors. The most common of these syndromes is multiple endocrine neoplasia type 1 (NEM1), a group of disorders that essentially includes pancreatic, pituitary, parathyroid and adrenal gland tumors. There are no known measures for preventing NETs.

Incidence

Neuroendocrine tumors (NETs) are rare, with 2 to 5 new cases per 100,000 people per year. They occur more frequently in older than in younger people. The average age at the time of diagnosis is about 65, and they affect men and women equally.