Neuroendocrine Tumors (NETs): Types, Symptoms, Diagnosis and Treatment (2026 Guide)

Medically reviewed content · Published 2026 · Last reviewed August 2026

A neuroendocrine tumor (NET) is a growth that starts in neuroendocrine cells — cells that share features of both hormone-producing endocrine cells and nerve cells. NETs can develop almost anywhere in the body, though the gastrointestinal tract, pancreas, and lungs are the most common sites.

Some NETs grow slowly over years; others behave aggressively. Some release hormones that cause specific symptoms (functional NETs); many do not (non-functional NETs). Because NETs vary so much by location, grade, and biology, there is no single “type” of NET and no single treatment path — diagnosis, grading, and staging together determine what a specific patient’s tumor means and how it should be managed.

This guide explains what NETs are, how they’re diagnosed and graded, the full range of current treatment options — including surgery, somatostatin analogues, PRRT with Lutetium-177 DOTATATE, targeted therapy, and liver-directed treatment and what NET care and its cost look like for international patients considering treatment in India. This is general medical education, not a diagnosis or a treatment recommendation for any individual reader.

Are Neuroendocrine Tumors Cancer?

Neuroendocrine tumors can be either benign or malignant, and the terminology itself reflects that range. A well-differentiated NET can be low-grade and slow-growing for years, sit at an intermediate grade, or less commonly be high-grade and aggressive while still classified as “well-differentiated.” A separate, more aggressive category, poorly differentiated neuroendocrine carcinoma (NEC), is always considered high-grade and behaves much more like other fast-growing cancers.

So the honest answer is: many NETs are cancer, some are indolent enough that they’re managed more like a chronic condition than an emergency, and a smaller subset (NEC) is aggressive cancer that needs urgent, intensive treatment. Grade and differentiation explained below — are what actually determine which category a specific tumor falls into.

NET, Neuroendocrine Carcinoma, and Carcinoid Tumor: What’s the Difference?

These three terms are often used loosely online, which creates confusion for patients trying to understand their own pathology report.

Well-differentiated neuroendocrine tumor (NET): Tumor cells still resemble normal neuroendocrine cells under the microscope and are organized in recognizable patterns. NETs are further divided into grades 1, 2, and 3 based on how fast the cells are dividing (see Grading below). Even grade 3 NETs remain, by definition, well-differentiated — a distinction that matters a great deal for treatment choice.

Poorly differentiated neuroendocrine carcinoma (NEC): Tumor cells no longer resemble organized neuroendocrine tissue. NEC is automatically classified as high-grade, tends to grow and spread faster, and is generally treated more like small-cell lung cancer than like a typical NET — usually with platinum-based chemotherapy as a starting point.

Carcinoid tumor: An older term, still used in some clinical settings and in patient-facing materials, that generally referred to well-differentiated NETs — most often in the gastrointestinal tract or lungs. Many tumors historically called “carcinoid” are today classified more precisely as well-differentiated NETs of a specific grade and site. The term isn’t wrong, but it shouldn’t be treated as interchangeable with every neuroendocrine neoplasm, and it says nothing about grade — a “carcinoid” could be low-grade or, less commonly, more advanced.

Where Do Neuroendocrine Tumors Develop?

NETs can arise almost anywhere neuroendocrine cells exist, but certain sites account for most cases:

• Stomach, duodenum, small intestine (jejunum/ileum), appendix, colon, and rectum — collectively gastrointestinal (GI) NETs
• Pancreas — pancreatic NETs (pNETs), arising from the hormone-producing islet cells
• Lungs and thymus — pulmonary and thymic NETs
• Less common sites — including the ovaries, testes, thyroid (medullary thyroid carcinoma is a related neuroendocrine cancer), and skin (Merkel cell carcinoma is a separate, distinct neuroendocrine cancer type)

Together, gastrointestinal and pancreatic NETs (GEP-NETs) are grouped clinically because their grading and staging systems overlap substantially. Lung and thymic NETs use a different classification framework, discussed further below. Treatment planning depends heavily on the primary site — a small-bowel NET and a pancreatic NET are managed very differently even when the biology looks superficially similar.

Functional vs. Non-Functional NETs

Functional NETs produce biologically active hormones in amounts large enough to cause a recognizable clinical syndrome. Examples include:

• Insulinoma (pancreas) — excess insulin causes hypoglycemia: sweating, tremor, confusion, weakness
• Gastrinoma (pancreas or duodenum) — excess gastrin causes recurrent peptic ulcers, abdominal pain, diarrhea (Zollinger-Ellison syndrome)
• Glucagonoma (pancreas) — causes hyperglycemia, a characteristic skin rash in some patients, and weight loss
• VIPoma (pancreas) — causes severe watery diarrhea and electrolyte abnormalities
• Somatostatinoma (pancreas) — associated with diabetes, gallstones, and diarrhea/fatty stools in some patients
• Serotonin-producing NETs (typically small bowel) — can cause carcinoid syndrome (flushing, diarrhea, wheezing) when serotonin and related substances reach the systemic circulation, most often once the tumor has spread to the liver

Non-functional NETs may still produce hormones or peptides at a biochemical level, but not in amounts that cause an obvious hormone syndrome. This is an important nuance: “non-functional” does not mean “produces nothing” — it means the tumor isn’t causing a recognizable hormone-driven illness. Non-functional NETs are often found incidentally, during imaging or endoscopy done for an unrelated reason, or once they’ve grown large enough to cause symptoms from mass effect (pain, obstruction, bleeding) rather than hormone effect.

Whether a NET is functional or non-functional does not, by itself, tell you how aggressive it is — that’s determined by grade and differentiation, not hormone production.

Symptoms of Neuroendocrine Tumors

Symptoms depend on the tumor’s location, size, whether it’s functional, and whether it has spread. Some NETs — particularly small, non-functional ones — cause no symptoms at all and are found incidentally during a colonoscopy, CT scan, or unrelated surgery.

Commonly reported symptoms include:

• Abdominal pain
• Diarrhea or a change in bowel habits
• Unexplained weight loss
• Nausea and vomiting
• Gastrointestinal bleeding
• Flushing (typically in carcinoid syndrome)
• Wheezing or a persistent cough (lung NETs)
• Recurrent low blood sugar episodes (insulinoma)
• Fatigue
• A new, growing lump

Symptoms by primary site

Symptoms alone cannot reliably identify the primary site or confirm a NET diagnosis — imaging and biopsy are required.

Carcinoid Syndrome and Carcinoid Heart Disease

Carcinoid syndrome typically occurs when serotonin and other biologically active substances from a NET — most often a small-bowel NET — reach the systemic circulation in large enough quantities, which usually happens once the tumor has spread to the liver (the liver normally breaks down these substances before they reach general circulation). Not every GI NET causes carcinoid syndrome; it’s specifically associated with serotonin-producing tumors with sufficient tumor burden, usually hepatic.

Symptoms include:

• Flushing, often of the face and upper body
• Diarrhea
• Wheezing or bronchospasm
• In advanced, longstanding cases, carcinoid heart disease

Carcinoid heart disease develops from chronic exposure of the right side of the heart to serotonin and related mediators, which can thicken and damage the tricuspid and pulmonary valves. It can cause shortness of breath, fatigue, and swelling (edema). Patients with significant, longstanding carcinoid syndrome are typically advised to have periodic cardiac assessment, since valve damage can progress silently before symptoms appear.

Management of carcinoid syndrome generally involves somatostatin analogues, treatment aimed at reducing overall tumor burden, and in select cases a medication called telotristat that reduces serotonin production; cardiac monitoring is added when carcinoid heart disease is a concern. This is general education — cardiac evaluation and treatment decisions require an individual specialist assessment.

Causes and Risk Factors

The exact cause of most neuroendocrine tumors isn’t known. NETs arise from acquired changes (mutations) in the DNA of neuroendocrine cells that cause abnormal, uncontrolled growth. A minority of cases are linked to inherited genetic syndromes, including:

• Multiple endocrine neoplasia type 1 (MEN1)
• Multiple endocrine neoplasia type 4 (MEN4)
• Von Hippel-Lindau (VHL) disease
• Neurofibromatosis type 1 (NF1)
• Tuberous sclerosis

More recent research has also identified associations with Lynch syndrome and SDH-related familial paraganglioma syndromes in some NET types. Patients with a strong family history of endocrine tumors, or a known inherited syndrome, may be offered genetic counseling and closer surveillance. For most patients, however, a NET occurs sporadically, with no identifiable inherited cause.

How Neuroendocrine Tumors Are Diagnosed

Diagnosis typically follows a structured pathway, though the exact sequence depends on how the tumor was first suspected (symptoms, incidental imaging finding, or hormone-related illness):

1. Clinical assessment and history
2. Laboratory and hormonal testing, where a functional syndrome is suspected
3. Imaging (CT, MRI, or somatostatin receptor PET/CT)
4. Endoscopy, where the GI tract is involved
5. Tissue biopsy
6. Pathology review — differentiation, grade, and Ki-67
7. Somatostatin receptor status assessment, where relevant to treatment planning
8. Staging

Blood and hormone tests

Testing is guided by the suspected syndrome and tumor site, not applied uniformly. Depending on clinical suspicion, tests may include chromogranin A, 24-hour urinary or plasma 5-HIAA (for suspected serotonin-producing NETs), gastrin, insulin/proinsulin/C-peptide (during a supervised hypoglycemia evaluation), glucagon, VIP, and somatostatin. Chromogranin A is a useful marker in the right clinical context, but it is not a definitive stand-alone diagnostic test — certain medications (notably proton pump inhibitors) and other medical conditions can raise it independent of any tumor. These tests should be ordered and interpreted by a treating physician, not self-ordered.

Imaging

• CT and MRI — identify tumor location, size, and evidence of spread, particularly to the liver
• Endoscopic ultrasound and endoscopy — used for GI tract and pancreatic NETs, and can allow biopsy at the same time
• Somatostatin receptor (SSTR) PET/CT — many well-differentiated NETs express somatostatin receptors on their cell surface. SSTR PET, most often using a Ga-68 DOTATATE tracer (Cu-64 DOTATATE is used in some centers), can identify disease sites throughout the body and helps determine whether a tumor is likely to respond to somatostatin-receptor-targeted treatments, including PRRT. Not every NET is somatostatin-receptor positive, so this scan doesn’t apply uniformly to all patients.
• FDG PET/CT — more useful in higher-grade, poorly differentiated, or more aggressive tumors, and in tumors with low somatostatin receptor expression. SSTR PET and FDG PET can be complementary rather than interchangeable — one isn’t universally “better” than the other; which is used (or whether both are used) depends on tumor grade and clinical question.

Biopsy and pathology

A tissue biopsy remains the standard for confirming a NET diagnosis. Pathologists assess differentiation, grade, Ki-67 proliferation index, mitotic activity, and necrosis, and use immunohistochemical markers commonly synaptophysin and chromogranin — to confirm neuroendocrine origin and help narrow down the likely primary site. Interpretation is always considered alongside imaging and clinical context, not in isolation.

Grade, Differentiation, and Staging

This is one of the most important and most misunderstood parts of a NET diagnosis.

Grade describes how the tumor is behaving biologically: specifically, how quickly the tumor cells are proliferating (dividing). Stage describes how far the disease has spread anatomically whether it’s confined to the original organ, has reached nearby lymph nodes, or has spread to distant sites like the liver or bone. Grade and stage are not the same thing and shouldn’t be used interchangeably: a lower-grade tumor can still be metastatic (spread to the liver, for example, while still dividing slowly), and a higher-grade tumor can be found at an earlier anatomical stage. Both, together, shape treatment decisions and prognosis.

What does Ki-67 mean?

Ki-67 is a protein marker pathologists use to estimate what percentage of tumor cells are actively dividing at the time the sample was taken — a proliferation index. For gastroenteropancreatic NETs, the current WHO/ENETS framework generally grades well-differentiated tumors as follows:

If a tumor is poorly differentiated on pathology, it’s automatically classified as high-grade neuroendocrine carcinoma (small-cell or large-cell type) — Ki-67 percentage doesn’t override that classification. Note also that these specific thresholds apply to gastroenteropancreatic NETs; lung and thymic NETs use a different framework, based primarily on mitotic count and the presence or absence of necrosis rather than a Ki-67 cutoff, distinguishing typical carcinoid, atypical carcinoid, large-cell neuroendocrine carcinoma, and small-cell lung cancer. Some pathology groups further subdivide G2 tumors (roughly 3%–10% vs. 10%–20%) because outcomes and treatment response can differ meaningfully within that range — ask your treating team whether this subgrading was applied to your report.

Staging

Staging is site-dependent — there is no single universal NET staging system. GI, pancreatic, and lung NETs each have their own TNM (tumor–node–metastasis) staging framework. Broadly, staging describes whether disease is localized to the primary organ, has spread to regional lymph nodes, or has spread to distant sites (most often the liver, and less commonly bone or lung). Your pathology and imaging reports, read together by your treating specialist, are what determine your specific stage — this guide can explain the concept but cannot assign a stage to any individual case.

Neuroendocrine Tumor Treatment: Overview

Treatment for neuroendocrine tumors (NETs) depends on the tumor’s location, grade, stage, differentiation, hormone production, somatostatin receptor status, and overall health. Options include:

• Surgery
• Active surveillance for selected small, low-grade tumors
• Somatostatin analogues such as octreotide and lanreotide
• PRRT with Lutetium-177 DOTATATE
• Targeted therapy
• Chemotherapy
• Liver-directed treatments
• Radiation therapy
• Immunotherapy in selected high-grade cases
• Supportive care

Surgery and Active Surveillance

Surgery can potentially cure localized NETs and may also help control selected metastatic disease, including removable liver metastases.

Active surveillance may be suitable for some small, low-grade, asymptomatic tumors. The decision depends on tumor size, grade, growth rate, location, and symptoms.

Somatostatin Analogues

Octreotide and lanreotide are used for hormone-related symptoms and can also slow tumor growth in selected well-differentiated, somatostatin-receptor-positive NETs.

PRRT

Peptide receptor radionuclide therapy (PRRT) uses radioactive medicine to target tumors that express somatostatin receptors. Lutetium-177 DOTATATE is widely used for appropriate progressive, receptor-positive NETs.

Treatment is usually given in multiple cycles. Kidney function and blood counts are monitored because possible side effects include nausea, fatigue, blood-count changes, and kidney effects. Rare long-term risks include blood disorders such as myelodysplastic syndrome.

Targeted Therapy and Chemotherapy

Targeted medicines such as everolimus and sunitinib are used for selected NETs.

Chemotherapy depends on tumor type. Poorly differentiated neuroendocrine carcinoma (NEC) is commonly treated with platinum-based chemotherapy, while selected pancreatic NETs may benefit from CAPTEM (capecitabine and temozolomide).

Immunotherapy has a more limited role and may be considered for selected high-grade, MSI-high/MMR-deficient tumors or clinical trials.

Liver Metastases

Treatment may include:

• Liver surgery
• Radiofrequency or microwave ablation
• TACE or TARE/SIRT
• PRRT
• Systemic therapy

The best approach depends on tumor distribution, liver function, tumor grade, and disease elsewhere in the body.

Prognosis

NET outcomes vary widely. Grade, Ki-67, tumor site, stage, liver involvement, receptor status, tumor growth rate, and treatment response all influence prognosis. A personalized assessment is more meaningful than a single survival percentage.

NET Treatment Cost in India

Why International Patients Consider India for NET Care, and How to Choose a Center

India has become one of the more active countries globally for PRRT and broader neuroendocrine oncology, with several centers reporting substantial PRRT case volumes and established nuclear medicine/theranostics programs. For international patients, the main draw is typically the combination of advanced diagnostic and treatment infrastructure — including SSTR PET/CT and PRRT capability, which aren’t universally accessible or affordable in every country — with costs that are generally lower than equivalent care in the US, UK, or much of Europe. That said, India should not be treated as automatically “the best” option for every patient; it’s one of several countries (including some in Southeast Asia and parts of Europe) with mature PRRT programs, and the right choice depends on an individual patient’s disease, budget, and travel considerations.

When evaluating a center for NET care in India or anywhere look for:

• Dedicated neuroendocrine oncology or multidisciplinary tumor board experience, not just general oncology
• In-house medical oncology, GI/pancreatic/hepatobiliary surgical expertise, and nuclear medicine under one roof
• SSTR PET/CT and, ideally, in-house PRRT capability rather than outsourcing
• Advanced pathology with reliable Ki-67 and IHC turnaround
• Liver-directed treatment capability (interventional radiology)
• Molecular testing access, where relevant
• Established international patient services (visa letters, coordination, interpreter support)
• Willingness to share prior NET case experience specifically — not just general cancer volume

Always verify accreditation, named specialist credentials, and PRRT capability directly with the hospital rather than relying solely on third-party listicles “top 10” rankings online are common in this space and are not a substitute for independent verification.

The International Patient Treatment Journey

1. Share existing pathology reports, imaging, and medical records for review
2. Confirm diagnosis, primary site, differentiation, and grade with the receiving team
3. Review Ki-67 and staging
4. Assess somatostatin receptor status, where relevant
5. Multidisciplinary tumor board consultation
6. Treatment plan proposed, with alternatives explained
7. Hospital and specialist confirmation
8. Written, itemized cost estimate
9. Medical visa guidance
10. Travel and accommodation arrangements
11. Treatment delivery
12. Response monitoring (imaging, bloodwork)
13. Discharge and recovery planning
14. Remote follow-up and report-sharing with the home-country physician

No credible provider can guarantee PRRT eligibility, treatment response, cure, an exact final cost, visa approval, or survival outcome before reviewing an individual patient’s full pathology and imaging — be cautious of any provider who offers these guarantees upfront.

How Shifam Health Helps International NET Patients

Shifam Health is a medical tourism facilitator, not a hospital, oncology clinic, nuclear medicine department, or pathology laboratory — we don’t diagnose neuroendocrine tumors or determine treatment plans. What we do is help international patients navigate the practical side of accessing NET care in India: coordinating the review of medical records and pathology by relevant specialists, helping shortlist hospitals with genuine neuroendocrine oncology and PRRT experience, obtaining written treatment and cost estimates, assisting with medical visa documentation, arranging airport pickup and accommodation, providing interpreter support where needed, and staying in touch for follow-up communication once a patient returns home.

You don’t need to have every answer before reaching out. If you’ve been told you or a family member has a neuroendocrine tumor and you’re trying to understand what treatment in India could look like, share your available reports with our team on WhatsApp or through a quick inquiry form — there’s no obligation, and we typically respond within 24 hours.

Frequently Asked Questions

People Ask Further Questions

Conclusion

“Neuroendocrine tumor” describes a genuinely diverse group of diseases, not a single condition with one expected course. Where the tumor starts, how differentiated it is, its grade and Ki-67, its stage, and its somatostatin receptor status together determine what a specific diagnosis means and which combination of surgery, somatostatin analogues, PRRT, targeted therapy, chemotherapy, or liver-directed treatment is appropriate. If you or someone you’re caring for has been diagnosed with a NET, understanding these distinctions and asking your care team direct questions about each one — is the most useful thing you can do before deciding on a treatment path, in India or anywhere else.

This article is for general medical education and does not replace individualized advice from a qualified oncologist, gastroenterologist, endocrinologist, or nuclear medicine specialist. It is not a diagnosis, treatment recommendation, or guarantee of any outcome.