Neuroendocrine Tumours (NETs)
Neuroendocrine tumours (commonly called NETs) are a group of growths that develop from neuroendocrine cells. These cells are scattered throughout the body. These cells share features of both nerve cells and hormone-producing cells, releasing chemical messengers that regulate digestion, breathing and metabolism. NETs most often arise in the pancreas, lungs and digestive tract; however, they can occur almost anywhere. Some tumours actively secrete hormones and cause distinctive symptoms, whereas others remain silent for years before being discovered incidentally. Behaviour ranges widely, from slow-growing tumours that cause few problems to aggressive forms that spread quickly. Because symptoms can be vague or mimic other conditions, NETs are sometimes diagnosed only after they have grown considerably or spread to other organs.
Types of Neuroendocrine Tumours
NETs are classified by the organ in which they arise, as location strongly influences symptoms and hormone activity. Different types are:
- Pancreatic NETs: These include insulinomas, gastrinomas and glucagonomas, each named for the hormone they overproduce.
- Gastrointestinal NETs: Sometimes called carcinoid tumours develop most often in the small intestine, appendix or rectum.
- Lung NETs: Also known as bronchial carcinoids, arise from neuroendocrine cells within the airways.
- Adrenal gland NETs: Pheochromocytoma and paraganglioma form in the adrenal glands or nearby nerve tissue and often secrete adrenaline-like hormones.
- Multiple endocrine neoplasia syndromes: They can cause NETs to develop in more than one gland simultaneously.
Causes of Neuroendocrine Tumours
Most NETs develop when neuroendocrine cells acquire genetic changes that allow them to grow beyond normal control. They are:
- Inherited changes in MEN1 gene mutations are strongly linked to pancreatic and parathyroid NETs.
- Von Hippel-Lindau disease increases the risk of pancreatic NETs as well as tumours in the kidney and central nervous system.
- Neurofibromatosis type 1 is associated with a higher risk of developing certain neuroendocrine tumours.
- Tuberous sclerosis complex carries a modestly increased risk of pancreatic NETs in affected individuals.
- The majority of cases occur sporadically, without any inherited syndrome or identifiable family pattern.
- Because the exact trigger for sporadic mutations remains unclear, no single environmental cause has been firmly established.
Signs & Symptoms of Neuroendocrine Tumours
Symptoms depend heavily on whether a tumour secretes hormones and if so, which hormone is involved. They are:
- Flushing and diarrhoea are hallmark features of carcinoid syndrome, caused by excess serotonin release.
- Episodes of low blood sugar including sweating and confusion can indicate an insulin-secreting pancreatic tumour.
- Recurrent peptic ulcers and abdominal pain may point to a gastrin-secreting tumour known as Zollinger-Ellison syndrome.
- Because many NETs grow slowly, unexplained weight loss and fatigue sometimes appear only after months of gradual change.
- Wheezing and shortness of breath can occur when a tumour affects the lungs or airways.
- Palpitations, high blood pressure and sweating episodes are typical of adrenaline-secreting tumours such as pheochromocytoma.
Risk Factors of Neuroendocrine Tumours
Several inherited conditions and demographic patterns raise the likelihood of developing a neuroendocrine tumour. They are:
- A diagnosis of MEN1 syndrome substantially increases lifetime risk across several glands.
- Most sporadic NETs are diagnosed between 50 and 70.
- Chronic conditions affecting stomach acid production have been linked to certain gastric NETs.
- Because smoking damages airway tissue, it has been associated with a higher risk of lung NETs.
Complication of Neuroendocrine Tumours
Complications from NETs can arise both from tumour growth and from the hormones they release:
- Carcinoid heart disease - long-term exposure to excess serotonin can damage heart valves over time.
- Liver metastasis is common in advanced gastrointestinal NETs and can worsen hormonal symptoms considerably.
- Severe hypoglycaemic episodes from insulin-secreting tumours can lead to seizures or loss of consciousness if untreated.
- Bowel obstruction may develop when a tumour or surrounding scar tissue narrows the intestine.
- Because a sudden surge of hormones can trigger a carcinoid crisis, this remains a serious risk during surgery or anaesthesia.
Diagnosis
Diagnosing NETs combines blood and urine testing, specialised imaging and tissue biopsy. Investigations are:
- Blood tests measuring chromogranin A to detect hormone-secreting activity typical of many NETs.
- Urine testing for 5-HIAA (a serotonin breakdown product) supports diagnosis of carcinoid syndrome.
- CT and MRI scans locate the primary tumour and assess whether disease has spread to other organs.
- Because NET cells often carry somatostatin receptors, specialised scans such as DOTATATE PET can pinpoint tumours precisely.
- A biopsy remains essential for confirming the diagnosis and grading how aggressively the tumour is likely to behave.
- Endoscopy allows direct visualisation and sampling of tumours within the digestive tract.
Treatment of Neuroendocrine Tumours
Treatment depends on tumour location, hormone activity and whether the disease has spread and often combines several approaches. They are:
- Surgery or removing the tumour offers the best chance of cure when the disease is localised.
- Somatostatin analogues control hormone-related symptoms and can slow tumour growth.
- Peptide receptor radionuclide therapy delivers targeted radiation directly to tumours that express somatostatin receptors.
- Targeted drugs block specific processes supporting tumour growth
- Some NETs behave aggressively; your doctor may use chemotherapy for higher-grade or rapidly progressing tumours.
- Liver-directed treatments (such as embolisation) help manage tumours that have spread to the liver.
When to see a doctor
Persistent or unusual symptoms linked to hormone activity should prompt timely medical assessment. They are:
- Recurrent flushing and diarrhoea that continue for weeks warrant assessment for carcinoid syndrome.
- Unexplained episodes of low blood sugar, especially with confusion or sweating, should never be dismissed
- Persistent abdominal pain or recurrent peptic ulcers warrant further investigation
- Because palpitations and sudden blood pressure spikes can indicate a hormone-secreting tumour, they warrant prompt review.
- Anyone with a family history of MEN1, Von Hippel-Lindau disease or neurofibromatosis should discuss screening with their doctor.
Conclusion
Neuroendocrine tumours form a diverse group of cancers, ranging from slow-growing to aggressive, united by their origin in hormone-producing cells. Early recognition of hormone-related symptoms can lead to earlier diagnosis and more effective treatment. Advances in targeted therapy and radionuclide treatment have improved outcomes for many patients in recent years. Because NETs can recur years after initial treatment, long-term monitoring remains an important part of care. A multidisciplinary approach combining surgery, medication and imaging offers the best overall management strategy.
FAQs
1. Are neuroendocrine tumours cancerous?
Neuroendocrine tumours can be either benign or cancerous, with behaviour ranging from slow-growing to aggressive and capable of spreading.
2. What are the common symptoms of neuroendocrine tumours?
Common symptoms include flushing, diarrhoea, abdominal pain, low blood sugar episodes and unexplained weight loss, depending on tumour location.
3. What tests are used to diagnose NETs?
Diagnosis includes blood and urine hormone testing, CT or MRI imaging, specialised somatostatin receptor scans and biopsy.
4. Is surgery used to treat neuroendocrine tumours?
Surgery is often used and offers the best chance of cure when the tumour is localised and has not spread.
5. Can neuroendocrine tumours come back after treatment?
NETs can recur even years after successful treatment, which is why long-term follow-up imaging is recommended.
6. How often should patients with NETs have follow-up?
Follow-up frequency varies by tumour grade, but most patients undergo imaging and hormone testing every six to twelve months.
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