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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Oncology · Neuroendocrine Neoplasms

Understanding Your Diagnosis: An Overview of Neuroendocrine Neoplasms (NENs)

At a Glance

Neuroendocrine neoplasms (NENs) are rare cancers that start in neuroendocrine cells. The most critical part of a new diagnosis is determining whether you have a slow-growing neuroendocrine tumor (NET) or a fast-growing neuroendocrine carcinoma (NEC), as this dictates your treatment.

If you have recently been diagnosed with a neuroendocrine neoplasm (NEN), you may feel like you are learning a new language while navigating an emotional whirlwind. This diagnosis often comes after months or even years of searching for answers, frequently involving misdiagnoses like irritable bowel syndrome (IBS), asthma, or menopause [1][2]. While the word “cancer” is frightening, understanding the biology of your specific diagnosis is the first step toward regaining control.

What are Neuroendocrine Neoplasms (NENs)?

Neuroendocrine neoplasms (NENs) are a group of rare cancers that arise from neuroendocrine cells [3]. These cells are unique because they act as “translators” between your nervous system and your endocrine (hormone) system. They are found throughout the body, most commonly in the lungs, stomach, and intestines [4].

Although NENs were once considered extremely rare, their incidence (the rate of new cases) has steadily increased over the last several decades [5][6]. This is partly because modern imaging, like endoscopy and CT scans, is better at finding these tumors than it used to be [7][8].

The Critical Distinction: NET vs. NEC

Your doctors will use two main categories to describe your diagnosis. The difference between them is vital because it determines your entire treatment path:

  1. Neuroendocrine Tumors (NETs): These are well-differentiated, meaning the cancer cells still look and act a lot like healthy neuroendocrine cells [9]. They are typically slower-growing.
  2. Neuroendocrine Carcinomas (NECs): These are poorly-differentiated, meaning the cells look very aggressive and abnormal under a microscope [10]. NECs are high-grade by definition and tend to grow and spread more rapidly [10][11].

Doctors use a marker called the Ki-67 index (a percentage that measures how fast cells are dividing) and the mitotic rate (the number of cells actively dividing in a sample) to grade the tumor [9][12].

Stabilizing Facts for Your Journey

It is natural to feel overwhelmed, but several facts can provide a foundation for your care:

  • Many NENs are slow-growing: Unlike many common cancers, many well-differentiated NETs are indolent (slow-growing), allowing patients to live with the disease for many years with high quality of life [3][5].
  • Advanced treatments exist: There has been a surge in new therapies, including peptide receptor radionuclide therapy (PRRT) and targeted biological drugs, which have significantly improved survival outcomes [5][13].
  • Expert care makes a difference: Research shows that survival is improving as management strategies evolve and more patients are treated by multidisciplinary teams (MDTs) who specialize in this specific disease [13][14].

The “Diagnostic Odyssey”

Many patients experience a “diagnostic odyssey”—a long period of being told their symptoms are something else. Because neuroendocrine cells can produce hormones, they may cause symptoms like flushing, diarrhea, or wheezing (sometimes called Carcinoid Syndrome) that mimic common ailments [3].

If you feel frustrated or angry about a delayed diagnosis, know that this is a common experience in the NEN community. The complexity of these tumors often requires specialized imaging (like SSTR PET-CT) and expert pathology to be correctly identified [15][16]. You are not alone, and finding a specialist who understands these nuances is a critical next step in your care.

Common questions in this guide

What is the difference between a NET and a NEC?
Neuroendocrine tumors (NETs) are typically slow-growing and look similar to healthy cells under a microscope. In contrast, neuroendocrine carcinomas (NECs) are highly aggressive, fast-growing cancers made of highly abnormal cells.
What does the Ki-67 index mean on my pathology report?
The Ki-67 index is a percentage that measures how fast the cancer cells are multiplying. Your care team uses this number, along with the mitotic rate, to grade your tumor and choose the most effective treatment plan.
Why do neuroendocrine tumors take so long to diagnose?
Because neuroendocrine tumors can release hormones into your bloodstream, they often cause general symptoms like flushing, diarrhea, or wheezing. These symptoms are frequently mistaken for common conditions like irritable bowel syndrome (IBS), asthma, or menopause, which delays the correct diagnosis.
What is Carcinoid Syndrome?
Carcinoid Syndrome is a collection of symptoms that occur when a neuroendocrine tumor produces excess hormones, such as serotonin. Common signs include unpredictable skin flushing, chronic diarrhea, and asthma-like wheezing.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Is my diagnosis a well-differentiated neuroendocrine tumor (NET) or a poorly-differentiated neuroendocrine carcinoma (NEC)?
  2. 2.What is the Ki-67 index and mitotic rate mentioned in my pathology report, and what do they mean for my treatment plan?
  3. 3.Are you a neuroendocrine specialist, or do you work with a multidisciplinary team (MDT) that includes one?
  4. 4.Is my tumor considered 'functional' (producing hormones like serotonin), and should I be tested for Carcinoid Syndrome?
  5. 5.What imaging or tests (like a Ga-68 DOTATATE PET/CT) are needed to accurately map the extent of the disease?

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 (16)
  1. 1

    Histopathological Features Predicting Neuroendocrine Morphology in Primary Breast Tumors: A Retrospective Analysis.

    Ozsen M, Senol K, Tolunay S, et al.

    European journal of breast health 2024; (20(2)):110-116 doi:10.4274/ejbh.galenos.2024.2023-12-10.

    PMID: 38571692
  2. 2

    Neuroendocrine Carcinomas of the Canine Mammary Gland: Histopathological and Immunohistochemical Characteristics.

    Nakagaki KYR, Nunes MM, Garcia APV, et al.

    Frontiers in veterinary science 2020; (7()):621714 doi:10.3389/fvets.2020.621714.

    PMID: 33469557
  3. 3

    Better Management for Neuroendocrine Neoplasms: A Complex Task Ahead.

    Coriat R

    Journal of clinical medicine 2021; (10(9)) doi:10.3390/jcm10091859.

    PMID: 33922910
  4. 4

    Sex Differences in the Survival of Patients with Neuroendocrine Neoplasms: A Comparative Study of Two National Databases.

    Mortagy M, El Asmar ML, Chandrakumaran K, Ramage J

    Cancers 2024; (16(13)) doi:10.3390/cancers16132376.

    PMID: 39001438
  5. 5

    Epidemiology of Neuroendocrine Neoplasms in the US.

    Dasari A, Wallace K, Halperin DM, et al.

    JAMA network open 2025; (8(6)):e2515798 doi:10.1001/jamanetworkopen.2025.15798.

    PMID: 40553474
  6. 6

    Epidemiologic trends of and factors associated with overall survival in patients with neuroendocrine tumors over the last two decades in the USA.

    Wu P, He D, Chang H, Zhang X

    Endocrine connections 2023; (12(12)).

    PMID: 37924638
  7. 7

    Neuroendocrine tumors of the appendix: a comprehensive review of the literature and case presentation.

    Vasile L, Barbu LA, Mogoş GFR, et al.

    Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie 2025; (66(2)):269-278 doi:10.47162/RJME.66.2.01.

    PMID: 40851238
  8. 8

    Advances in Endoscopic Diagnosis and Treatment of Gastric Neuroendocrine Neoplasms.

    Guo X, Zhao X, Huang G, Yu Y

    Digestive diseases and sciences 2024; (69(1)):27-35 doi:10.1007/s10620-023-08180-0.

    PMID: 37971578
  9. 9

    Emerging Therapeutic Concepts and Latest Diagnostic Advancements Regarding Neuroendocrine Tumors of the Gynecologic Tract.

    Georgescu TA, Bohiltea RE, Munteanu O, et al.

    Medicina (Kaunas, Lithuania) 2021; (57(12)) doi:10.3390/medicina57121338.

    PMID: 34946283
  10. 10

    An analysis of 130 neuroendocrine tumors G3 regarding prevalence, origin, metastasis, and diagnostic features.

    Kasajima A, Konukiewitz B, Schlitter AM, et al.

    Virchows Archiv : an international journal of pathology 2022; (480(2)):359-368 doi:10.1007/s00428-021-03202-6.

    PMID: 34499237
  11. 11

    Challenges in High-grade Neuroendocrine Neoplasms and Mixed Neuroendocrine/Non-neuroendocrine Neoplasms.

    La Rosa S

    Endocrine pathology 2021; (32(2)):245-257 doi:10.1007/s12022-021-09676-z.

    PMID: 33786701
  12. 12

    Neuroendocrine Neoplasms of the Gynecologic Tract.

    Virarkar M, Vulasala SS, Morani AC, et al.

    Cancers 2022; (14(7)) doi:10.3390/cancers14071835.

    PMID: 35406607
  13. 13

    Epidemiology, treatment and outcomes of gastroenteropancreatic neuroendocrine neoplasms.

    Uhlig J, Nie J, Gibson J, et al.

    Scientific reports 2024; (14(1)):30536 doi:10.1038/s41598-024-81518-4.

    PMID: 39690170
  14. 14

    ENETS standardized (synoptic) reporting for endoscopy in neuroendocrine tumors.

    Borbath I, Pape UF, Deprez PH, et al.

    Journal of neuroendocrinology 2022; (34(3)):e13105 doi:10.1111/jne.13105.

    PMID: 35233848
  15. 15

    Treatment modalities favoring outcome in well-differentiated neuroendocrine tumors G3.

    Hinterleitner M, Pfeiffer R, Trautwein NF, et al.

    Frontiers in endocrinology 2023; (14()):1285529 doi:10.3389/fendo.2023.1285529.

    PMID: 38260136
  16. 16

    Multimodal management of foregut neuroendocrine neoplasms.

    Zhou Y, Li JW, Uedo N

    Best practice & research. Clinical gastroenterology 2024; (68()):101889 doi:10.1016/j.bpg.2024.101889.

    PMID: 38522885

This page provides a general overview of neuroendocrine neoplasms for educational purposes. Always consult your oncologist or a specialized NEN multidisciplinary team for a formal diagnosis and treatment plan tailored to your specific condition.

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