Gastric neuroendocrine cancer, also called a gastric neuroendocrine tumour (gastric NET/ gNET), gastric neuroendocrine neoplasm (gNEN) or gastric neuroendocrine carcinoma (gNEC), is a rare type of stomach cancer that starts in specialised neuroendocrine cells within the stomach lining.
These cells help regulate digestion and stomach acid production. The most common of these are enterochromaffin-like (ECL) cells, which respond to the hormone gastrin.
Gastric NETs were previously known as gastric carcinoid tumours. Today, the term gastric neuroendocrine cancers is more commonly used because it better reflects how these tumours are classified, diagnosed, and treated. Gastric neuroendocrine cancers can be classified based on how the tumour cells appear under the microscope. Well-differentiated tumours are known as neuroendocrine tumours (NETs) and are typically slower growing, whereas poorly differentiated tumours are classified as neuroendocrine carcinomas (NECs), which tend to behave more aggressively. Most gastric NETs, particularly Type 1 and Type 2 tumours, are slow growing, while Type 3 tumours and poorly differentiated neuroendocrine carcinomas (NECs) are more likely to spread to lymph nodes or other organs.
At NeuroEndocrine Cancer Australia (NECA), we support people diagnosed with gastric neuroendocrine cancer and their families through education, resources, advocacy, and access to the NET Nurse service.
The stomach contains neuroendocrine cells that help control stomach acid and digestive function. In some people, these cells grow abnormally and form tumours.
A key hormone involved in many gastric NETs is gastrin. Gastrin tells the stomach to produce acid. When gastrin levels remain high over a long period of time, ECL cells can become overstimulated and may form multiple small tumours.
This is why some gastric NETs are called gastrin-dependent. Others develop without high gastrin levels and can behave quite differently.
Because gastric NETs vary so much, accurate classification is important. The tumour type, size, grade, Ki-67 index, and stage all help guide treatment and follow-up.
Gastric NETs are usually grouped into four clinical subtypes.
Type 1 gastric NETs are the most common type. They are usually linked to chronic autoimmune atrophic gastritis.
In autoimmune atrophic gastritis, the immune system damages the stomach’s acid-producing cells. As stomach acid levels fall, the body produces more gastrin. High gastrin levels can then stimulate ECL cells and lead to the development of small gastric NETs.
Type 1 gastric NETs are usually:
They are often found during gastroscopy. Treatment may involve endoscopic removal and regular monitoring, especially because new small tumours can develop over time.
Type 2 gastric NETs are rare and occur in association with Multiple Endocrine Neoplasia type 1 (MEN1), where gastrin secreting tumours (gastrinomas) cause excessive acid production, resulting in Zollinger–Ellison syndrome.
Type 2 gastric NETs are often:
People with Type 2 gastric NETs may need monitoring for MEN1 and other endocrine tumours. Genetic counselling may also be recommended.
Type 3 gastric NETs are sporadic. This means they are not usually linked to high gastrin levels, autoimmune gastritis, or MEN1.
They are more likely to be:
Type 3 gastric NETs are usually treated more actively than Type 1 and Type 2 tumours. Surgery is often recommended when the tumour can be removed.
Poorly differentiated gastric neuroendocrine carcinomas (NECs) were historically sometimes referred to as ‘Type 4’ gastric neuroendocrine tumours, although this is not part of the formal WHO classification system.
Type 4 gastric neuroendocrine cancers are very rare, and are usually poorly differentiated neuroendocrine carcinomas.
These cancers can grow quickly and behave more aggressively than well-differentiated gastric NETs. They may be small cell or large cell neuroendocrine carcinomas.
Treatment often involves a more intensive approach, which may include chemotherapy, surgery, radiotherapy, or other systemic therapies depending on the stage and overall health of the person.
The cause of gastric neuroendocrine cancer depends on the type.
Risk factors may include:
People with autoimmune atrophic gastritis may also have pernicious anaemia or vitamin B12 deficiency. These are associated conditions that share the same underlying cause, rather than risk factors in themselves.
Long-term proton pump inhibitor use can increase gastrin levels. Any possible relationship between long-term PPI use and gastric NET risk should be discussed with a treating specialist.
Gastric NETs can affect the body in different ways depending on their type.
In rare cases, advanced gastric NETs may cause hormone-related symptoms, particularly if the cancer has spread to the liver.
Many gastric NETs cause no symptoms in the early stages. They are often found during gastroscopy for reflux, anaemia, abdominal pain, or investigation of another stomach condition.
When symptoms occur, they may include:
Some people may also experience symptoms related to carcinoid syndrome, such as flushin and, diarrhoea,. This is uncommon in gastric NETs but can occur if functional tumour cells spread to the liver.
In gastric NETs, this flushing is often described as atypical. It may appear bright red and patchy and may relate more to histamine release than serotonin.
Diagnosing gastric NETs usually involves endoscopy, biopsy, blood tests, pathology, and imaging.
A gastroscopy allows doctors to examine the stomach lining using a thin flexible camera. Small tumours or polyps may be seen and removed or sampled during the procedure.
A biopsy is important because it confirms whether the cells are neuroendocrine in origin.
Pathologists examine the tumour under a microscope. They usually test for neuroendocrine markers such as:
They also assess the Ki-67 index, which shows how quickly the tumour cells are dividing.
The tumour grade helps describe how fast the cancer is likely to grow.
| Grade | Ki-67 index | What it usually means |
| Grade 1 | Less than 3% | Slower-growing |
| Grade 2 | 3 – 20% | Moderate growth rate |
| Grade 3 | Greater than 20% | Faster-growing |
Ki-67 thresholds are interpreted alongside tumour type, differentiation and other pathological features.
Blood tests may include fasting gastrin levels, vitamin B12, iron studies, and other markers depending on the suspected tumour type.
Gastrin levels can help distinguish Type 1 and Type 2 gastric NETs from Type 3 tumours.
Imaging is used to assess tumour size and whether cancer has spread.
Tests may include:
The most appropriate imaging depends on the tumour type and grade.
Treatment depends on the tumour type, size, grade, location, and whether it has spread.
A multidisciplinary team may include a gastroenterologist, surgeon, medical oncologist, endocrinologist, nuclear medicine specialist, dietitian, pathologist, radiologist, and NET nurse.
Small Type 1 and Type 2 gastric NETs can often be removed during endoscopy.
This may be suitable when tumours are:
Regular follow-up is usually needed because Type 1 tumours can recur.
Very small, low-risk Type 1 gastric NETs may sometimes be monitored rather than removed immediately.
Surveillance may involve repeat gastroscopy every 12 to 24 months, depending on the person’s risk factors and specialist advice.
Surgery may be recommended for larger tumours, higher-risk tumours, or Type 3 gastric NETs.
Surgery may involve:
The type of surgery depends on tumour size, depth, location, and stage.
Somatostatin analogues, such as octreotide or lanreotide, may be used in select people with advanced or functional NETs.
They may help:
Chemotherapy may be used for aggressive, poorly differentiated, high-grade or metastatic gastric neuroendocrine cancers.
Other treatments may include targeted therapies or peptide receptor radionuclide therapy (PRRT), depending on tumour biology, receptor status, and specialist recommendation.
If gastric NETs spread to the liver, liver-directed therapies may be considered in selected cases.
These can include embolisation, chemoembolisation, ablation, or other targeted approaches depending on the number, size, and location of liver metastases.
Living with gastric NETs can involve ongoing monitoring, treatment decisions, symptom management, and emotional adjustment.
Some people with Type 1 gastric NETs live well for many years with periodic endoscopy and management of associated conditions such as vitamin B12 deficiency or anaemia.
People with more aggressive gastric NETs may need more frequent scans, specialist review, and treatment for advanced disease.
Good supportive care can make a significant difference. This may include nutrition support, psychological care, symptom management, and connection with others who understand neuroendocrine cancer.
Type 1 gastric NETs are often linked to autoimmune atrophic gastritis. This condition can affect the stomach cells that help absorb vitamin B12.
Low vitamin B12 can cause pernicious anaemia and may lead to:
Some people need lifelong vitamin B12 injections or high-dose supplements. Iron levels may also need monitoring.
Dietary needs vary depending on the tumour type, treatment, and whether stomach surgery has been performed.
After partial or total gastrectomy, people may need to adjust how they eat. Some may experience dumping syndrome, where food moves too quickly into the small intestine.
Helpful strategies may include:
People with ongoing diarrhoea, weight loss, low iron, or low B12 should seek specialist nutrition support.
Follow-up depends on the tumour type and risk level.
Low-risk Type 1 & 2 tumours may be monitored with repeat gastroscopy every 12 months.
Higher-risk Type 3 or Type 4 tumours may require more frequent follow-up, including CT, MRI, PET imaging, blood tests, and specialist review.
The aim of surveillance is to detect recurrence or new tumour growth, monitor nutritional complications, and adjust management if the disease changes over time.
Research into gastric neuroendocrine cancer continues to improve diagnosis, treatment, and long-term care.
Important areas of development include:
Clinical trials may be available for some people, particularly those with advanced or treatment-resistant disease.
A diagnosis of gastric neuroendocrine cancer can feel overwhelming, especially when the disease is rare and difficult to understand.
NECA provides support for people affected by NETs, including:
For support, information, and guidance after a gastric NET diagnosis, contact NeuroEndocrine Cancer Australia.
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