Neuroendocrine cancers are uncommon but far less rare than most people assume. In the United States, about 8.5 new cases per 100,000 people are diagnosed each year, which translates to roughly 28,000 new diagnoses annually. That puts them in an awkward middle ground: too rare for most general practitioners to think of them first, but common enough that over 170,000 Americans were living with a neuroendocrine tumor diagnosis as of 2014. What makes them especially tricky is that the incidence has been climbing steeply for decades, and yet the average patient still waits years for a correct diagnosis.
A Five-Fold Rise in Diagnoses Since the 1970s
The recorded incidence of neuroendocrine neoplasms (NENs) in the U.S. increased roughly five-fold between 1975 and 2021, from about 1.6 per 100,000 people to about 8.5 per 100,000.1JAMA Network Open. Epidemiology of Neuroendocrine Neoplasms in the US A separate analysis focused on the 2000–2018 window found the incidence climbing from roughly 4.9 to 8.2 per 100,000, with an annual percentage change of about 3.4%.2PubMed Central. Epidemiologic trends of and factors associated with overall survival in patients with neuroendocrine tumors over the last two decades in the USA England saw a parallel trend: incidence rose from 2.5 to 8.8 per 100,000 between 1995 and 2018, an absolute increase of 371%.3The Lancet Regional Health – Europe. Incidence and survival of neuroendocrine neoplasia in England 1995–2018: A retrospective, population-based study
The biggest jumps have been in early-stage, well-differentiated tumors. In the U.S. data spanning 1975 to 2021, localized-stage tumors rose about 13-fold, and well-differentiated tumors rose about 53-fold.1JAMA Network Open. Epidemiology of Neuroendocrine Neoplasms in the US That pattern strongly suggests that better imaging, more frequent endoscopies and colonoscopies, and improved pathological classification are catching tumors that would have been missed or mislabeled a generation ago. It does not mean these cancers are spreading through the population like an epidemic; it means we got better at finding them, especially the slow-growing ones.
Still, the rise is not entirely an artifact of detection. Incidence went up across all stages and grades, including advanced disease. Whether a genuine biological increase is happening alongside the diagnostic shift remains an open question, but the detection explanation accounts for much of the trend.
Where in the Body They Appear
Neuroendocrine cells are scattered throughout the body, so these tumors can form almost anywhere. In practice, the gastrointestinal tract and the pancreas account for the majority. In the U.S. SEER database, the highest incidence rates for specific organ sites were about 3.6 per 100,000 for gastroenteropancreatic tumors and about 1.5 per 100,000 for lung tumors.4JAMA Oncology. Trends in the incidence, prevalence, and survival outcomes in patients with neuroendocrine tumors in the United States Within the digestive system, the pancreas, rectum, and stomach are the three most common locations.5PubMed Central. Clinicopathological heterogeneity between primary and metastatic sites of gastroenteropancreatic neuroendocrine neoplasm An older German referral-center series found that among gastroenteropancreatic neuroendocrine tumors, about 44% originated in the foregut (with the pancreas alone accounting for about 29%), another 44% in the midgut (mostly the small bowel), and only about 4% in the hindgut.6PubMed. Survival and clinical outcome of patients with neuroendocrine tumors of the gastroenteropancreatic tract in a german referral center
The lung is the second most common site overall. About a quarter of all primary lung tumors have neuroendocrine features, though the vast majority of those are high-grade small cell lung cancers, which behave very differently from the slow-growing carcinoid tumors most people picture when they hear “neuroendocrine.”7PubMed Central. Challenges in the Diagnosis and Management of Well-Differentiated Neuroendocrine Tumors of the Lung (Typical and Atypical Carcinoid) Low-grade carcinoid tumors of the lung, by contrast, make up only about 2% of all lung tumors, and the atypical (intermediate-grade) carcinoid is rarer still.8PubMed Central. Atypical carcinoid tumor of the lung: A rare entity
Then there are the genuinely unusual locations. Case series have documented neuroendocrine tumors arising in the breast, ovary, uterine cervix, vulva, kidney, sinonasal tract, extrahepatic bile ducts, and thymus, among others.9PubMed Central. Neuroendocrine Neoplasms in Rare Locations: Clinicopathological Features and Review of the Literature These are extraordinarily rare individually, but they matter because a tumor in an unexpected location is even easier to misdiagnose.
The Long Road to Diagnosis
One of the most striking things about neuroendocrine tumors is how long patients typically wait between their first symptoms and a correct diagnosis. In a large patient-reported survey, the median time from first symptom to diagnosis was nearly 54 months, and 80% of respondents had visited their primary care doctor about their symptoms a median of 11 times before getting the right answer. Many were initially told they had irritable bowel syndrome or dyspepsia.10PubMed Central. Delays and routes to diagnosis of neuroendocrine tumours A real-world analysis using insurance claims data found that about 70% of patients with a neuroendocrine tumor had received a prior misdiagnosis of a gastrointestinal, respiratory, metabolic, or skin condition, with a median time from earliest potential misdiagnosis to correct NET diagnosis of about 3.4 years.11Surgical Oncology Insight. Real-world analysis of neuroendocrine tumor misdiagnosis and associated costs A separate study using machine learning on claims data confirmed the 70% misdiagnosis figure.12PubMed. Exploration of machine learning techniques to examine the journey to neuroendocrine tumor diagnosis with real-world data
The reasons for these delays are not hard to understand. Many neuroendocrine tumors grow slowly and produce vague symptoms: intermittent abdominal pain, flushing, diarrhea, wheezing. None of those screams “cancer” to a doctor, and all of them overlap with extremely common, benign conditions. The rarity of neuroendocrine tumors relative to those common diagnoses means they are rarely the first thing a clinician suspects.
Functional Tumors and Hormonal Syndromes
Some neuroendocrine tumors secrete hormones and other biologically active substances, producing recognizable syndromes. These are called functional tumors. Among pancreatic neuroendocrine tumors, roughly 35% are functional.13PubMed Central. Pancreatic neuroendocrine tumors with transformation to insulinoma: an unusual presentation of a rare disease The most common functional type in the pancreas is the insulinoma, which causes dangerous drops in blood sugar by secreting excess insulin. Insulinomas are quite rare on an absolute scale, with an annual incidence of roughly 4 per million.14International Journal of Surgery Case Reports. Pancreatic insulinoma: Diagnosis and treatment of a rare tumour with misleading symptoms Other functional pancreatic types, like glucagonoma, gastrinoma, and VIPoma, are even scarcer. In one large Chinese series of 286 patients with functional pancreatic neuroendocrine neoplasms spanning 20 years, insulinomas dominated at 266 cases, followed by glucagonoma at 10, with all other subtypes in the single digits.15PubMed Central. Clinical Characteristics and Management of Functional Pancreatic Neuroendocrine Neoplasms: A Single Institution 20-Year Experience with 286 Patients
Outside the pancreas, the best-known hormonal syndrome is carcinoid syndrome, caused by functional tumors (usually in the small bowel or appendix) that release serotonin and other vasoactive substances. The hallmark symptoms are flushing, diarrhea, and sometimes wheezing. In the past, up to half of patients with carcinoid syndrome developed carcinoid heart disease, a form of valve damage driven by serotonin. More recent data suggest the prevalence of carcinoid heart disease has dropped to around 20% or less, likely because of earlier detection and better treatment.16PubMed Central. Management of Diarrhea in Patients With Carcinoid Syndrome
For patients living with a functional tumor, the hormonal symptoms can be as disabling as the cancer itself. Severe diarrhea, unpredictable flushing episodes, and blood sugar swings can reshape daily life in ways that non-functional tumors of the same size and stage might not.
How Doctors Find and Track Them
Two advances have reshaped the diagnostic landscape for neuroendocrine tumors over the past decade or so. The first is molecular imaging, specifically PET/CT scans using gallium-68-labeled somatostatin analogues. These scans home in on somatostatin receptors, which most well-differentiated neuroendocrine tumors express in abundance. Gallium-68 DOTATATE PET/CT has shown superior lesion detection compared to older techniques like octreotide scintigraphy (the “OctreoScan”), MIBG scintigraphy, and MRI.17PubMed Central. The value of (68)Ga-DOTATATE PET/CT in diagnosis and management of neuroendocrine tumors compared to current FDA approved imaging modalities: a review of literature This scan does not just find the primary tumor; it maps metastases throughout the body and helps oncologists decide whether a patient is a candidate for targeted radionuclide therapy.
The second tool is the blood marker chromogranin A (CgA), a protein released by neuroendocrine cells. It has been the standard circulating biomarker for these tumors, especially those arising in the digestive tract and pancreas.18PubMed Central. Chromogranin A as a valid marker in oncology: Clinical application or false hopes? A meta-analysis of its diagnostic performance found a sensitivity of about 73% and a specificity of about 95%.19PLOS ONE. Diagnostic Value of Circulating Chromogranin A for Neuroendocrine Tumors: A Systematic Review and Meta-Analysis That high specificity means an elevated CgA is a useful flag, but the moderate sensitivity means a normal CgA does not rule out a neuroendocrine tumor. Proton pump inhibitors (common heartburn drugs) can also raise CgA levels, creating false alarms in patients who happen to be taking them.
Well-Differentiated vs. Poorly Differentiated
The term “neuroendocrine cancer” covers a wide biological spectrum, and the distinction between well-differentiated and poorly differentiated tumors is the single most important clinical dividing line. Well-differentiated neuroendocrine tumors (sometimes called NETs) tend to grow slowly, retain many features of normal neuroendocrine cells, and can sometimes be managed for years even when they have spread. Poorly differentiated neuroendocrine carcinomas (NECs) are aggressive, fast-dividing tumors with a much worse prognosis and a different treatment approach.20Neoplasia. Nothing But NET: A Review of Neuroendocrine Tumors and Carcinomas
This matters for interpreting rarity statistics. Small cell lung cancer, one of the most lethal cancers, is technically a high-grade neuroendocrine carcinoma. It is not rare at all. When people talk about neuroendocrine tumors being uncommon, they are usually referring to the well-differentiated ones: carcinoid tumors, pancreatic NETs, and similar slow-growing subtypes. The well-differentiated tumors make up the bulk of the rising incidence trend, while the poorly differentiated carcinomas have not changed much in frequency. So when you hear that neuroendocrine tumor diagnoses have multiplied fivefold, that growth is concentrated in the less aggressive end of the spectrum.
Genetic Syndromes That Raise Risk
Most neuroendocrine tumors arise sporadically, without a clear hereditary cause. But a fraction are linked to inherited genetic syndromes. The most well-known are multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2 (MEN2), and von Hippel-Lindau syndrome (VHL).21PubMed. Molecular genetics of neuroendocrine tumors MEN1 predisposes to tumors of the parathyroid glands, the pituitary, and the pancreas; pancreatic neuroendocrine tumors develop in a substantial proportion of MEN1 patients over their lifetimes. MEN2 is most associated with medullary thyroid carcinoma and pheochromocytoma, both of which are neuroendocrine in nature. VHL raises the risk of pancreatic neuroendocrine tumors along with kidney cancer and other tumors.
For patients with these syndromes, neuroendocrine tumors are not rare at all: they are an expected part of lifelong surveillance. This is one reason genetic counseling and testing matter. A young person diagnosed with a pancreatic neuroendocrine tumor, for instance, should be evaluated for MEN1 if there is any family history of endocrine tumors, parathyroid disease, or pituitary adenomas.
Treatment Has Evolved Considerably
Surgery remains the primary treatment when a neuroendocrine tumor is localized and can be completely removed. But for tumors that have spread or cannot be resected, a targeted treatment called peptide receptor radionuclide therapy (PRRT) has become a game-changer. PRRT uses a radioactive isotope, most commonly lutetium-177, attached to a somatostatin analogue that binds to receptors on the tumor cells, delivering radiation directly where it is needed. A systematic review and meta-analysis found a disease control rate of about 78–79% with lutetium-177 DOTATATE, with relatively mild side effects such as fatigue and nausea.22PubMed Central. The efficacy of (177)Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) in patients with metastatic neuroendocrine tumours: a systematic review and meta-analysis Results from Korean patients with advanced tumors were consistent with outcomes seen in the pivotal Western clinical trials, suggesting the treatment works across populations.23PubMed. Efficacy and Safety of Lu-177 DOTATATE Peptide Receptor Radionuclide Therapy in Patients with Unresectable or Metastatic Neuroendocrine Tumors in Korea
The same gallium-68 PET/CT scan used for diagnosis doubles as a screening tool for PRRT eligibility: if the scan lights up, it confirms the tumor has the somatostatin receptors the therapy targets. This pairing of diagnostic imaging with a matched treatment is sometimes called a “theranostic” approach, and neuroendocrine tumors are one of the best-established examples in oncology.
Racial Differences in Incidence and Outcomes
Neuroendocrine tumors do not affect all racial groups equally. U.S. data show that Black patients have a higher incidence across all stages, with the largest gap at the localized stage: about 4.3 per 100,000 compared to 2.6 per 100,000 in White patients.24PubMed. Racial Differences in the Incidence and Survival of Patients With Neuroendocrine Tumors Despite this higher incidence, and despite having clinical features often associated with a better prognosis, Black patients with distant-stage disease had worse survival. The study found that socioeconomic and sociodemographic factors, rather than tumor biology alone, contributed to the disparity. This is consistent with patterns seen across many cancer types: access to specialists, timely follow-up imaging, and insurance coverage all shape outcomes in ways that track with race in the U.S.
The Day-to-Day Burden
Living with a neuroendocrine tumor affects more than physical health. In a large U.S. patient survey, nearly three-quarters of patients reported at least a moderate negative impact on their lives, and almost 40% described the impact as large. The most commonly reported effects were on energy levels (71%), finances (59%), and emotional health (58%). About two-thirds of patients made dietary changes because of their tumor, 60% reported increased spending on travel (often for specialized care), and 57% cut back on physical activities.25PubMed Central. Patient-Reported Experience of Diagnosis, Management, and Burden of Neuroendocrine Tumors: Results From a Large Patient Survey in the United States
Work life takes a hit as well. Among patients who were employed at the time of the survey, 62% had to take days off, 21% worked reduced hours, and 16% stopped working entirely for a period. Of those who were on medical disability, 79% said their neuroendocrine tumor was the reason.25PubMed Central. Patient-Reported Experience of Diagnosis, Management, and Burden of Neuroendocrine Tumors: Results From a Large Patient Survey in the United States The financial toll is compounded by the rarity of the disease itself: patients often need to travel to specialized centers, and treatments like PRRT are not available everywhere.
Neuroendocrine Tumors in Children
Neuroendocrine tumors are genuinely rare in the pediatric population. When they do appear, the clinical picture looks different from adults. A systematic review covering more than 3,800 pediatric patients found the appendix was the most common tumor site (30%), followed by the adrenal gland (19%), pancreas (19%), and lungs (14%).26PubMed. Management and outcomes of pediatric neuroendocrine tumors – A systematic review of published studies Girls were slightly more often affected than boys. A substantial proportion of appendiceal neuroendocrine tumors in children are discovered incidentally during appendectomies performed for appendicitis, which means they are caught early almost by accident.
Among pediatric patients with malignant neuroendocrine tumors specifically, one U.S. study identified 481 cases and found the breakdown included malignant carcinoid (39%), central nervous system tumors with neuroendocrine features (26%), medullary thyroid carcinoma (18%), and neuroendocrine carcinoma (10%), among others.27PubMed. Malignant neuroendocrine tumors: incidence and outcomes in pediatric patients The diversity of subtypes reflects how the neuroendocrine classification cuts across traditional organ-based cancer categories, linking tumors that arise in very different parts of the body under a shared cellular identity.