Navigating Your Neuroendocrine Carcinoma (NEC) Diagnosis
On This Page:
I've Just Been Diagnosed With NEC
"Poorly differentiated neuroendocrine carcinoma" is a lot to take in, let alone understand. If you or someone you love has just been diagnosed with a NEC, you might feel frightened, overwhelmed, numb, or even relieved to finally have a name for what’s been happening. There isn’t one right way to feel.
This page won’t tell you what your diagnosis means for you personally. That’s a conversation to have with your care team. What this page can do is help you make sense of the words, explain how NEC differs from a grade 3 neuroendocrine tumor (NET), and give you a starting point for conversations ahead.
First, We Are Here to Help
A new diagnosis can bring a rush of unfamiliar terms, tests, and appointments. You do not have to understand everything today.
It may help bring someone you trust to appointments, write down questions as they come up, and ask for copies of your reports. NCF's Newly Diagnosed page has more practical tips for getting organized.
What the Words Mean
Each part of "poorly differentiated neuroendocrine carcinoma" tells your care team something about the cancer:
-
Neuroendocrine refers to the type of cells the cancer began in. Neuroendocrine cells are found throughout the body and can produce hormones.
-
Carcinoma is a term for cancer that begins in cells that line or cover organs and passages.
-
Poorly differentiated describes how the cancer cells look under a microscope. Unlike well-differentiated cells, they look very different from normal neuroendocrine cells.
-
High-Grade describes how quickly the cells are dividing. Your team will likely use a measurement called Ki-67 to help assess this.
NEC is both poorly differentiated and high-grade. Those terms are related, but they do not mean the same thing. A tumor can be high-grade and still be well differentiated.
NEC and Grade 3 NET
A well-differentiated grade 3 neuroendocrine tumor, or G3 NET, is also high-grade. The difference is that its cells still look relatively like normal neuroendocrine cells under a microscope. NEC cells do not.
These are different diagnoses. They can behave differently and may need different treatments. That’s why the exact wording in your pathology report matters, and why an article about “high-grade” neuroendocrine cancer may not necessarily be describing your diagnosis.
What's Next
Your next steps will depend on your situation, but many people have conversations like these with their care team:
-
Confirming the pathology. Your pathology report helps guide the treatment plan. Ask whether it identifies the cancer as a poorly differentiated NEC, whether it is small cell or large cell, and what the Ki-67 result is. NEC can be difficult to distinguish from other tumors on a small biopsy, so it is reasonable to ask whether a pathologist with neuroendocrine experience has reviewed it.
-
Finding out where the cancer is. Scans such as CT, MRI, or PET may help show where the cancer started and whether it has spread. The scans you need will depend on your situation. Sometimes the original site cannot be found, but your team can often still make a treatment plan.
-
Learning more about the tumor. Your team may recommend molecular testing to look for features that could affect treatment or clinical trial options.
-
Making a treatment plan. Recommendations depend on where the cancer began, whether it has spread, your pathology, your overall health, and what matters to you. NEC treatment often includes therapy that works throughout the body, such as chemotherapy. Radiation or surgery may also be part of the plan. Because NEC is rare and can grow quickly, care teams often move promptly and bring in specialists from several fields.
-
Getting expert input. Experts recommend seeking care, or at least a second opinion, at a center experienced with high-grade neuroendocrine cancers. You can ask whether that review can happen quickly or alongside treatment planning, rather than delaying it.
Know What You Don't Know
You don’t need to ask all of these at once. Choose the ones that feel most useful for your next appointment:
-
Does my report say poorly differentiated NEC? Is it small cell or large cell? What is my Ki-67?
-
Has a pathologist with neuroendocrine experience reviewed my biopsy?
-
Where did the cancer start, and how far has it spread? What tests do I still need?
-
Do you recommend molecular testing for my tumor?
-
What treatments do you recommend, and what is the goal of each?
-
How soon do we need to begin? Can I get a second opinion at the same time?
-
Are there clinical trials I might be eligible for?
-
What side effects should I expect, and who should I call if I have a problem?
-
What support is available for me and my family?
Learning to Live With the Unknowns
NEC is a serious cancer. It is understandable to want answers about what comes next, but outlook varies from person to person. Statistics online may group different diseases together or use older ways of classifying them. They describe groups of people, not what will happen to one individual.
If you want to talk about what your diagnosis may mean for you, your care team is the right place to start. If you’re not ready for that conversation yet, that’s okay too.
You also do not have to navigate this alone. Neuroendocrine Cancer Foundation (NCF) is here for you and your family. You can contact the Support Line, explore NEC Resources, including podcasts, and a Facebook group, browse the Clinical Trials Guide, connect with a peer through NETCONNECT, or join a support group. Talking with someone who understands can make the next step feel a little less lonely.
This page is for education only and does not replace advice from your care team.
Understanding Poorly Differentiated Neuroendocrine Carcinoma (NEC)
If your pathology report says “poorly differentiated neuroendocrine carcinoma,” or NEC, you may already have noticed that much of the information you find about neuroendocrine tumors (NETs) does not seem to fit. That is because NEC and the well-differentiated NETs you may read about are different diagnoses.
This page explains what the words in your report mean, how NEC differs from a well-differentiated grade 3 NET, why an accurate pathology diagnosis matters, and what you can ask your care team. NEC is a serious diagnosis, but no two people have the same situation or treatment path.
What is NEC?
Understanding the Pathology
NEC is Not the Same as G3 NET
Why the Precise Diagnosis Matters
Neuroendocrine neoplasm, or NEN, is an umbrella term for cancers that begin in neuroendocrine cells. These cells are found throughout the body and can produce hormones. NENs fall into two main groups: well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs).
NEC is uncommon. It can begin in the digestive tract, pancreas, lung, female reproductive organs, urinary tract, or elsewhere. Sometimes tests cannot identify where it began. You may hear your team call this an unknown primary.
Compared with most NETs, NEC tends to grow and spread more quickly. It is also generally treated differently. That is why knowing the exact diagnosis, not just that a cancer is “neuroendocrine”, matters.
Note: NEC is also not adenocarcioma, which you typically hear associated with pancreatic or colon cancers.
A pathologist is a doctor who examines tissue from a biopsy or surgery. When looking at a neuroendocrine cancer, they consider two different questions: What do the cells look like, and how quickly are they dividing?
Differentiation describes how much the cancer cells still resemble normal neuroendocrine cells. Well-differentiated cells look relatively organized and recognizable. Poorly differentiated cells look much more abnormal and disorganized.
Grade describes how quickly the cells are dividing. Pathologists may assess this using the Ki-67 index, the percentage of cells showing signs of division, and/or a count of cells seen dividing under a microscope. Grades range from 1 (low) to 3 (high). Grade 3 generally means a Ki-67 above 20%, although grading details vary somewhat by where the cancer began.
NEC is, by definition, both poorly differentiated and high-grade, or G3. But high-grade does not always mean poorly differentiated. Some well-differentiated NETs are also grade 3.
Your report may describe NEC as small cell or large cell, based on how the cells look under a microscope. It may also mention another type of cancer alongside the NEC in the same tumor. This is sometimes called a mixed neuroendocrine–non-neuroendocrine neoplasm, or MiNEN. If you see that term, ask your team what it means for your treatment plan.
A well-differentiated grade 3 NET, often shortened to G3 NET, has cells that still resemble normal neuroendocrine cells but are dividing quickly. NEC has cells that are poorly differentiated. Both diagnoses are high-grade, but they can behave differently and often call for different treatment approaches.
For a G3 NET, doctors may consider some treatments also used for other NETs. NEC is more often treated with chemotherapy similar to that used for small-cell lung cancer. Information about “high-grade neuroendocrine cancer” may refer to either diagnosis, so it is worth checking which one a resource or study is discussing.
Distinguishing them is not always simple. Ki-67 results can overlap, especially when there is only a small biopsy sample. Pathologists also consider how the cells look, the results of special stains, and other features.
Your pathology report is the foundation for decisions about treatment, scans, and clinical trials. To make the diagnosis, pathologists may use special stains, called immunohistochemistry, to confirm that a tumor is neuroendocrine. They also assess Ki-67 and study the appearance of the cells.
Small biopsies can be difficult to interpret, and neuroendocrine pathology is a specialty. It is reasonable to ask whether a pathologist with experience in neuroendocrine neoplasms has reviewed your tissue, and whether an expert second review would be helpful.
Ask for a copy of your pathology report. You do not have to interpret it on your own, but you can ask your team to point out whether it says “poorly differentiated,” whether it specifies small cell or large cell, and where to find the Ki-67 result.
Tests You May Hear About
Testing is tailored to the person and the tumor. You may not need every test on this list. Ask your team what each recommended test is meant to answer and whether its result could change the plan.
Your team may discuss some of the following:
Imaging
CT and MRI scans can help show where the cancer is and whether it has spread. A PET scan may also be useful in some situations. Somatostatin receptor PET scans, sometimes called DOTATATE PET, are commonly discussed in NET care but are not always needed for newly diagnosed NEC. A different PET scan, called FDG PET, may be used in certain circumstances. Brain imaging is usually considered when there are symptoms or extensive disease.
Molecular Testing
This examines features of the tumor that may affect treatment or clinical trial options. Ask whether it is recommended, when results are expected, and whether treatment should begin while you wait.
Endoscopy or
Colonoscopy
Your team may recommend these if they suspect the cancer began in the digestive tract.
Blood Tests
Markers often followed in NET, such as chromogranin A, are generally not useful for monitoring NEC. Your team will usually rely on scans to assess how treatment is working.
Genetic Counseling
NEC is not generally linked to an inherited syndrome. If you have a family history of cancer or concerns about inherited risk, ask whether genetic counseling makes sense for you.
How Treatment Is Planned
Treatment depends on where the NEC began, whether it has spread, the details of your pathology, your overall health, and your goals.
Because NEC can spread early, treatment usually includes systemic therapy, treatment that works throughout the body, even when scans show cancer in only one area. This most often means chemotherapy. A common combination is a platinum drug, either cisplatin or carboplatin, with etoposide. Other combinations, such as cisplatin with irinotecan, are sometimes used.
NEC is rare, and there have been relatively few large trials focused specifically on it. As a result, some treatment recommendations draw on small-cell lung cancer research and expert consensus.
If the cancer appears to be localized, your team may discuss chemotherapy, radiation, surgery, or a combination. Whether surgery is helpful depends in part on where the tumor began, and experts do not always agree on its role. That is one reason a review by specialists from several fields, a multidisciplinary team, can be valuable.
Immunotherapy and newer targeted approaches, including treatments aimed at a protein called DLL3, are being studied in clinical trials. Whether a trial is an option for you depends on your diagnosis, tumor features, treatment history, and the trial’s eligibility rules. NCF’s Clinical Trials Guide includes NEC studies, but it is not a complete list of trials; bring any study you find to your care team to discuss whether it fits your situation.
Some treatments commonly used for NET, such as somatostatin analogs and peptide receptor radionuclide therapy (PRRT), are generally not used for NEC. That does not mean you are receiving less care. It means the plan is being shaped around how NEC behaves.
NEC can progress quickly, so ask your team how soon treatment should begin. If you would like another expert to review your case, ask whether that can happen alongside treatment planning rather than delaying it.
Questions for Your Care Team
You do not have to ask every question at once. Bring the ones that matter most to your next appointment, and return to the others as you learn more.
-
Does my pathology report say poorly differentiated NEC, well-differentiated G3 NET, or something else? What is my Ki-67?
-
If it is NEC, is it small cell or large cell? Is there another cancer component in the tumor, such as MiNEN?
-
Who reviewed my pathology? Would an expert second review help?
-
Do we know where the cancer started? If the primary site is unknown, does that change the plan?
-
How far has the cancer spread? Which scans or tests do I still need, and which can wait?
-
Do you recommend molecular testing of my tumor? When should we expect the results?
-
What treatment options do you recommend, and what is the goal of each?
-
How soon should treatment start? Can an expert opinion be obtained at the same time?
-
Are surgery or radiation options for me? Why or why not?
-
Are there clinical trials I might qualify for now or later?
-
What side effects should I expect? Whom do I call if I have a problem, and how will we know whether treatment is working?
-
What supportive care and emotional support are available for me and my family?
Living With Uncertainty
A serious diagnosis can bring frightening questions, including questions about the future. You may come across statistics that are difficult to read. Some are based on older ways of classifying these cancers; others group diseases that we now understand differently. Even a statistic that describes NEC cannot predict what will happen to one person.
If you want to discuss what is known about your outlook, ask your care team to put the information in the context of your own diagnosis. If you do not want to focus on numbers right now, that is okay too.
You do not have to navigate this alone. Experts in high-grade neuroendocrine cancers recommend seeking care, or at least an opinion, at a center experienced with these diagnoses. Ask whether an expert review can happen quickly and in parallel with your current team’s planning.
What's On The Horizon For NEC?
If you or someone you love is living with poorly differentiated neuroendocrine carcinoma (NEC), you may be wondering whether research is bringing new options closer. There is meaningful work underway, particularly on treatments designed to target features of NEC cells. There is also an important distinction to keep in mind: most of these approaches are still being studied, and promising early results are not the same as a proven treatment.
This is a plain-language look at what researchers are asking, what we know so far, and what we still need to learn.
First, a note on terms
This section is about poorly differentiated NEC, not well-differentiated neuroendocrine tumors (NETs), including grade 3 NETs. They are different diagnoses, and research findings for one do not automatically apply to the other.
Trial populations can make this confusing. Some studies include small cell lung cancer (SCLC); others focus on NEC that starts outside the lung, called extrapulmonary NEC. Some include both NEC and G3 NET. As you read about a study, it helps to check exactly who was included.
Where treatment stands today
For advanced extrapulmonary NEC, the usual first treatment is platinum-based chemotherapy with etoposide. This approach draws in part on experience treating SCLC, because large studies dedicated to NEC have been limited. Chemotherapy can shrink or stabilize the cancer for many people, but its effects often do not last.
There is no single second-line treatment that has clearly been shown to work best for everyone. Much of today’s research is focused on that gap.
Treatments Researchers Are Studying
Targeting DLL3. DLL3 is a protein found on many NEC cells, though not every tumor has it or has it at the same level. Researchers are studying several ways to use DLL3 as a target:
-
T-cell engagers connect a DLL3-bearing cancer cell to an immune T cell. Tarlatamab is approved for previously treated extensive-stage SCLC, but not for NEC outside the lung; NEC trials are underway. Another T-cell engager, obrixtamig, showed encouraging activity in an early study that included several cancer types. Researchers are now studying it after prior treatment in DLL3-high extrapulmonary NEC in DAREON-5, and with standard chemotherapy in advanced extrapulmonary NEC in DAREON-NEC-1.
-
Antibody-drug conjugates, or ADCs, use an antibody to deliver a cancer-fighting drug to cells carrying DLL3. One of these, zocilurtatug pelitecan, or “zoci,” has received FDA Fast Track designation for previously treated extrapulmonary NEC. Some tumors shrank in a small early group. Fast Track is intended to speed development; it is not an approval or proof that a drug works.
-
Radioligand approaches aim to deliver radiation to DLL3-bearing cells. These are at an earlier stage of research.
The questions are whether these treatments help people live longer than standard care, how durable any responses are, and who is most likely to benefit. T-cell engagers can also cause serious immune-related effects, including cytokine release syndrome and neurologic symptoms, so monitoring by an experienced team matters. NCF’s Clinical Trials Guide includes information on DLL3 studies in NEC.
Immunotherapy
Adding atezolizumab to chemotherapy improved survival in a large SCLC trial. Whether that benefit extends to NEC outside the lung is not yet known. The SWOG S2012 trial is studying that question, including whether continuing immunotherapy after chemotherapy helps. For now, expert consensus guidance does not recommend adding immunotherapy to first-line chemotherapy routinely for extrapulmonary NEC.
Other immunotherapy combinations have helped some people in small studies, but those studies included both NEC and G3 NET, making it difficult to know who benefits. An early trial is also testing an oncolytic virus called SVV-001 with two checkpoint inhibitors in people with NEC or G3 NET. Its first priority is understanding safety and dosing. NCF lists both SWOG S2012 and the SVV-001 study in its trial guide.
Matching treatment to the tumor
Some testing is already useful in care today. Expert consensus supports checking NEC tumors for mismatch repair (MMR) or microsatellite instability (MSI) status, along with broader genetic sequencing. A small proportion of NECs have features, such as MSI-high or MMR-deficient status, or rare NTRK or RET gene fusions, that may open the door to treatments approved across cancer types in certain circumstances.
Other findings are less clear-cut. BRAF V600E mutations occur in some colorectal NECs, and case reports describe responses to BRAF-targeted treatment. One study found potentially targetable changes in about two-thirds of NEC samples, but “potentially targetable” does not mean a treatment has been proven to help in NEC. Blood tests for tumor DNA, called ctDNA, remain investigational. DLL3 testing is also being used to determine eligibility for certain trials.
What Trials Are Trying to Answer
Researchers are asking several practical questions:
-
Does adding a new drug to first-line chemotherapy improve outcomes? Trials include SWOG S2012 and DAREON-NEC-1.
-
What treatment works best after first-line chemotherapy? DLL3-targeted trials are one part of that search.
-
For NEC that has not spread, what combination of chemotherapy, radiation, and surgery works best? The French NEONEC trial is one example.
-
Can biomarkers help identify which treatment is most likely to help a particular person?
These answers take time. NEC is rare, and enrolling enough people in trials can be difficult.
At a Glance
Bringing Research Into Your Care
A clinical trial may be worth discussing, but it is not the right choice for everyone. Participation is voluntary, standard treatment remains a valid choice, and you can leave a trial at any time. If you want to explore your options, these questions can help:
-
Has my tumor had molecular testing? What did it show, and would DLL3 testing be relevant?
-
Are there trials for my specific diagnosis, where my cancer started, and the treatments I’ve already had?
-
What are the eligibility requirements? Are there timing windows we need to know about?
-
How do the possible benefits and risks compare with standard treatment?
-
What would participation mean for appointments, travel, and costs?
-
Would a second opinion at a neuroendocrine cancer center help us review the options?
You can explore NCF’s Clinical Trials Guide, which includes NEC studies, and search registries such as ClinicalTrials.gov. NCF notes that its guide is not a complete list of trials, so bring anything you find to your care team to discuss whether it fits your situation.
There is reason to be hopeful that researchers are asking more precise questions about NEC. It is just as important to be honest about where the evidence stands today. Your care team can help you weigh established treatment against a clinical trial, with your diagnosis, priorities, and circumstances at the center of that decision.
Resources for NEC
Educational Videos
High Grade NETs
High Grade NETs
Novel Targeted Therapies in Neuroendocrine Cancers • 2026 NCF Event • Mar 9, 2026
The Latest on Immunotherapy for Neuroendocrine Cancer • 2025 NCF Event • Dec 11, 2025
"Large Cell Neuroendocrine Carcinoma & Small Cell Lung Cancer" • Session B • LACNETS • Dec 10, 2024
Podcast Episodes
Extrapulmonary neuroendocrine carcinoma (EP-NEC) is a rare and complex cancer that can be difficult to recognise, diagnose, and treat. This short video helps patients and care partners understand the disease, including what to expect from diagnosis and treatment, the urgency needed, and where support is available. It is designed to help patients and their families navigate this challenging condition.
Click here for more information >>>
In this video podcast by COR2ED, Neuroendocrine Patient Advocate Susan Meckler-Plummer joins Medical Oncologist Dr. Aman Chauhan to discuss extra-pulmonary neuroendocrine carcinomas (EP-NECs).
DLL3 is emerging as a promising new target for neuroendocrine cancers. In this episode, Dr. Rohit Thummalapalli, medical oncologist at Memorial Sloan Kettering Cancer Center, explains what DLL3 is, how it works, who might benefit, and what current clinical trials are teaching us. He breaks down the science, treatment options, and future directions in a way that is clear, approachable, and designed to help patients and families better understand this developing area of care.
What are Grade 3 Poorly Differentiated Neuroendocrine Carcinoma (NEC)? What makes NEC unique? Can a NET transform to NEC? Dr. Nitya Raj from Memorial Sloan Kettering Cancer Center in New York City explains NEC tumor biology and how it guides treatment strategy. She also discusses current clinical trials and research.
Facebook Group
For more information & and support, contact high-grade patient advocate Susan Meckler Plummer, who supported her late husband with NEC.
Susan Meckler Plummer
609-731-0322