Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 15 peer-reviewed journal articles Updated
Gastroenterology · Gastric Neuroendocrine Tumor

The Three Types: Why Your Subtype Defines Your Journey

At a Glance

Gastric neuroendocrine tumors (G-NETs) are divided into three main subtypes that determine a patient's prognosis. Type 1 is slow-growing and driven by autoimmune gastritis. Type 2 is linked to MEN1 syndrome. Type 3 is sporadic, does not rely on gastrin, and is the most aggressive.

The most critical piece of information in your diagnosis is your subtype. While they all occur in the stomach, the three primary types of gastric neuroendocrine tumors (G-NETs) are essentially different diseases with different biological “engines” and very different outcomes [1][2].

Type 1: The Autoimmune-Driven Type

Type 1 is the most common form, accounting for 70% to 80% of all cases [3].

  • The Cause: It is driven by chronic autoimmune atrophic gastritis, a condition where the immune system attacks the stomach lining. This causes the stomach to lose its ability to make acid [4][5].
  • The Mechanism: To compensate for the lack of acid, the body floods the system with a hormone called gastrin. Gastrin acts like a “growth fertilizer” for the ECL cells in the stomach, causing them to grow into small, usually multiple, tumors [4][6].
  • Outlook: These are typically slow-growing (indolent) and have an excellent prognosis, with a very low risk of spreading [7][8].

Type 2: The Hormone-Secreting Type

Type 2 is rare, making up about 5% to 10% of cases [1].

  • The Cause: These occur in patients with Zollinger-Ellison syndrome, often as part of a genetic condition called MEN1 (Multiple Endocrine Neoplasia type 1) [1][9].
  • The Mechanism: Unlike Type 1, these patients have too much stomach acid because a separate tumor (a gastrinoma, usually in the pancreas or duodenum) is pumping out massive amounts of gastrin [10][6].
  • Outlook: While they are also driven by gastrin, their behavior depends on the management of the underlying syndrome [2].

Type 3: The Sporadic Type

Type 3 accounts for 10% to 15% of cases and is the most serious form [3].

  • The Cause: These are “sporadic,” meaning they occur randomly and are not caused by high gastrin levels or autoimmune disease [3][1].
  • The Mechanism: Because they aren’t waiting for a “hormone signal” to grow, they are biologically more aggressive and have a much higher malignant potential (risk of spreading to the liver or lymph nodes) [3][7].
  • Outlook: These require more intensive treatment, often involving surgery similar to other cancers, because they are often diagnosed at a higher grade [3][11].

The Emerging Type 4: PPI-Associated

Recent research has identified a potential fourth group in patients who have used Proton Pump Inhibitors (PPIs)—common acid-blockers—for many years [12][13].

  • The Theory: Long-term PPI use can mimic the “no acid” environment of Type 1, leading to high gastrin levels that trigger tumor growth [14].
  • Current Consensus: These appear to be slow-growing and non-aggressive. While not yet universally included in all official classification systems, many specialists now consider them a distinct, low-risk subgroup that may improve if the medication is adjusted [12][13].
    WARNING: Do not abruptly stop or alter your PPI medication without direct medical supervision. Stopping PPIs suddenly can cause severe rebound acid hypersecretion.

Identifying Your Type at a Glance

Feature Type 1 Type 2 Type 3
Gastrin Level Very High [4] Very High [6] Normal [3]
Stomach Acid Very Low [4] Very High [10] Normal [3]
Number of Tumors Multiple [5] Multiple [1] Usually Single [3]
Metastatic Risk Very Low (<2-5%) [15] Low to Moderate [1] High (up to 50%+) [3]
Underlying Issue Autoimmune [4] MEN1 Syndrome [9] None (Sporadic) [3]

Understanding which category you fall into is the first step toward a personalized care plan. Most patients will have Type 1, which allows for a much more conservative and “watchful” approach to care [8][15].

Common questions in this guide

What is a Type 1 gastric neuroendocrine tumor?
Type 1 is the most common and least aggressive form of gastric neuroendocrine tumor. It is driven by chronic autoimmune atrophic gastritis, which lowers stomach acid and causes your body to produce too much gastrin. This extra gastrin triggers the tumors to grow.
How is a Type 3 gastric neuroendocrine tumor different from Type 1?
Unlike Type 1, Type 3 tumors are sporadic, meaning they occur randomly and are not linked to high hormone or gastrin levels. They are biologically more aggressive than Type 1 and have a much higher risk of spreading, usually requiring more intensive treatment like surgery.
Can long-term antacid or PPI use cause stomach tumors?
Recent research suggests long-term use of proton pump inhibitors, or PPIs, may create a low-acid environment that triggers slow-growing, non-aggressive stomach tumors known as Type 4. You should never stop your PPI medication abruptly without consulting your doctor, as this can cause severe rebound acid symptoms.
What role does gastrin play in gastric neuroendocrine tumors?
Gastrin is a hormone that can act like a growth fertilizer for certain stomach cells. In Type 1 and Type 2 tumors, abnormally high gastrin levels directly drive the growth of these neuroendocrine tumors in the stomach.
Why is it important to know my G-NET subtype?
It is very important because the subtypes are essentially different diseases. Most patients have Type 1, which has a very low risk of spreading and allows for a watchful approach, whereas Type 3 requires immediate, aggressive treatment.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my lab results, is my tumor 'gastrin-dependent' (Type 1 or 2) or 'sporadic' (Type 3)?
  2. 2.What was my Ki-67 percentage, and how does it affect my risk of metastasis?
  3. 3.If I have Type 1, should we also be checking my B12 levels or thyroid function for other autoimmune conditions?
  4. 4.If I have been on PPIs for years, could this be the newer 'Type 4' diagnosis, and how should we safely manage my medications?
  5. 5.Given my subtype, is surgery necessary, or can we manage this with periodic endoscopies?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (15)
  1. 1

    A 15-year experience with gastric neuroendocrine tumors: Does type make a difference?

    Postlewait LM, Baptiste GG, Ethun CG, et al.

    Journal of surgical oncology 2016; (114(5)):576-580 doi:10.1002/jso.24369.

    PMID: 27393718
  2. 2

    GASTRIC NEUROENDOCRINE TUMOR: REVIEW AND UPDATE.

    Dias AR, Azevedo BC, Alban LBV, et al.

    Arquivos brasileiros de cirurgia digestiva : ABCD = Brazilian archives of digestive surgery 2017; (30(2)):150-154 doi:10.1590/0102-6720201700020016.

    PMID: 29257854
  3. 3

    Neuroendocrine Tumors of the Stomach.

    Corey B, Chen H

    The Surgical clinics of North America 2017; (97(2)):333-343 doi:10.1016/j.suc.2016.11.008.

    PMID: 28325190
  4. 4

    Unmasking the high-risk phenotype in autoimmune gastritis: A pathologist's roadmap for the clinician.

    Wang CL, Zeng M, Luo Y

    World journal of gastroenterology 2025; (31(48)):115244 doi:10.3748/wjg.v31.i48.115244.

    PMID: 41480315
  5. 5

    The changing face of chronic autoimmune atrophic gastritis: an updated comprehensive perspective.

    Massironi S, Zilli A, Elvevi A, Invernizzi P

    Autoimmunity reviews 2019; (18(3)):215-222 doi:10.1016/j.autrev.2018.08.011.

    PMID: 30639639
  6. 6

    Gastric Neuroendocrine Tumors (Carcinoids).

    Gluckman CR, Metz DC

    Current gastroenterology reports 2019; (21(4)):13 doi:10.1007/s11894-019-0684-7.

    PMID: 30868284
  7. 7

    Management of Gastric Neuroendocrine Tumors: A Review.

    Sok C, Ajay PS, Tsagkalidis V, et al.

    Annals of surgical oncology 2024; (31(3)):1509-1518 doi:10.1245/s10434-023-14712-9.

    PMID: 38062290
  8. 8

    Management of type 1 gastric neuroendocrine tumors: an 11-year retrospective single-center study.

    Chen YY, Guo WJ, Shi YF, et al.

    BMC gastroenterology 2023; (23(1)):440 doi:10.1186/s12876-023-03079-6.

    PMID: 38097952
  9. 9

    Case report: optimal tumor cytoreduction and octreotide with durable disease control in a patient with MEN-1 and Zollinger-Ellison syndrome-over a decade of follow-up.

    Daniels LM, Khalili M, Morano WF, et al.

    World journal of surgical oncology 2019; (17(1)):213 doi:10.1186/s12957-019-1758-6.

    PMID: 31818296
  10. 10

    Gastrinomas: Medical or Surgical Treatment.

    Norton JA, Foster DS, Ito T, Jensen RT

    Endocrinology and metabolism clinics of North America 2018; (47(3)):577-601 doi:10.1016/j.ecl.2018.04.009.

    PMID: 30098717
  11. 11

    Gastric carcinoids: Does type of surgery or tumor affect survival?

    Crown A, Kennecke H, Kozarek R, et al.

    American journal of surgery 2019; (217(5)):937-942 doi:10.1016/j.amjsurg.2018.12.057.

    PMID: 30686481
  12. 12

    Gastric neuroendocrine tumors arising from chronic proton pump inhibitor use: characteristics and outcomes of a fourth subtype.

    Egbert LK, Kartik A, Wasif N, et al.

    Journal of gastrointestinal surgery : official journal of the Society for Surgery of the Alimentary Tract 2025; (29(11)):102207 doi:10.1016/j.gassur.2025.102207.

    PMID: 40961542
  13. 13

    The Association Between Proton Pump Inhibitor Use and Gastroenteropancreatic Neuroendocrine Tumors: A Systematic Review.

    Moeinipour Y, Abedi F, Sadeghi M, et al.

    Journal of gastrointestinal cancer 2025; (56(1)):214 doi:10.1007/s12029-025-01328-3.

    PMID: 41191220
  14. 14

    Gastric neuroendocrine tumours from long-term proton pump inhibitor users are indolent tumours with good prognosis.

    Trinh VQ, Shi C, Ma C

    Histopathology 2020; (77(6)):865-876 doi:10.1111/his.14220.

    PMID: 32702178
  15. 15

    Last decade of advances in gastric neuroendocrine tumors: Innovations, challenges, and future directions.

    Christodoulidis G, Kouliou MN, Ragias D, et al.

    World journal of clinical oncology 2025; (16(5)):104577 doi:10.5306/wjco.v16.i5.104577.

    PMID: 40503415

This page explains gastric neuroendocrine tumor subtypes for educational purposes only. Always consult your gastroenterologist or oncologist for diagnosis, subtype confirmation, and a personalized care plan.

Get notified when new evidence is published on Neuroendocrine tumor of stomach.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.