This page was reviewed under our medical and editorial policy by
Maurie Markman, MD, President, Medicine & Science.
This page was updated on August 29, 2022.
Neuroendocrine tumors (NETs) form in cells that interact with the nervous system or in glands that produce hormones. These cells, called neuroendocrine cells, can be found anywhere in the body, but NETs are most often found in the abdomen, especially in the gastrointestinal tract. These tumors may also be found in the lungs, pancreas and adrenal glands. Merkel cell cancer, a type of skin cancer, is also categorized as a neuroendocrine cancer.
All NETs are considered malignant (cancerous) tumors. Most NETs take years to develop and grow slowly. However, some NETs may be fast-growing.
More than 12,000 NETs are diagnosed each year in the United States, accounting for a small fraction of the number of new cancer cases. But more and more Americans are being diagnosed with the disease, with incidence rates rising markedly over the past 15 years.
In addition to being rare, NETs are complex and may be difficult to diagnose. In fact, most people aren’t diagnosed with a neuroendocrine tumor until they’ve already experienced symptoms for more than four years. This type of delay can be frustrating. That’s why it’s important to seek care from trained oncologists with expertise in neuroendocrine tumor diagnoses and treatments. At City of Hope, our multidisciplinary team of cancer experts has training and experience in diagnosing and treating all stages of neuroendocrine tumors.
Neuroendocrine tumors are such an important focus at City of Hope that each of our hospitals has a GI Cancer Center dedicated to treating patients with all stages of gastrointestinal diseases. Our gastroenterologists and oncologists understand the complexities of neuroendocrine tumors.
They work with you to create an individualized treatment plan that includes evidence-based treatments and technologies to fight neuroendocrine cancer, combined with supportive care services to help reduce side effects and keep you strong in body, mind and spirit.
This overview will cover the basic facts about neuroendocrine tumors, including:
If you believe you may be experiencing symptoms of neuroendocrine cancer and want to schedule an appointment for diagnostic testing, or if you’re interested in a second opinion on your neuroendocrine tumor diagnosis and treatment plan, call us or chat online with a member of our team.
There is no one cause or specific risk factor associated with NETs. There are, however, factors that may raise a person’s risk for developing a NET, including:
Inherited syndromes: Multiple endocrine neoplasia type 1 (MEN1) is a hereditary condition associated with certain types of NETs, including NETs, GI tract NETs, and pancreatic NETs. Other hereditary conditions related to NETs include Von Hippel-Lindau syndrome, neurofibromatosis type 1, multiple endocrine neoplasia type 2 (MEN2), and tuberous sclerosis complex.
Other medical conditions: Certain diseases can put people at greater risk of developing specific types of NETs. For example, people with diseases that damage the stomach and reduce acid production have a greater risk of developing a NET of the stomach.
Environment and diet: Based on known data, there is no connection between NETs and the environment or diet.
Statistically, whites are more likely to develop an NET than other ethnic groups. Also, for unknown reasons, NETs are slightly more common in women than in men.
"We called the toll-free number to inquire about a second opinion. Even from that first phone call, I felt well cared for. There were no voice prompts to wade through or shuttling from one person to the next. After meeting with the care team, I had a CT scan and was walked through a proposed treatment plan a day or so later. "
NETs can begin in any part of the body, including the:
Doctors may classify a NET tumor by its site of origin, such as GI NET, pancreatic NET or lung NET. NET tumors are almost always considered to be malignant or cancerous.
Symptoms associated with an NET depend on the location of the tumor, and whether the NET is found to be functional or nonfunctional. Functional NETs are categorized by the presence of clinical symptoms due to excess hormone secretion by the tumor. Nonfunctional NETs do not secrete hormones. They may produce symptoms caused by the tumor’s growth.
Common neuroendocrine tumor symptoms include:
Like many cancers, the symptoms of NETs can be similar to those caused by other, non-cancerous conditions, which may lead to a misdiagnosis or a delayed diagnosis. That’s why many NETs are diagnosed at an advanced stage.
Staging is a way of describing where the tumor is located, if or where it has spread, and whether it is affecting other parts of the body. Neuroendocrine tumor staging is key in developing the appropriate treatment plan. Diagnostic testing is used by doctors to determine the stage of a NET tumor and to better predict a patient’s prognosis. There are different stage descriptions for different types of NETs.
NETs may:
The World Health Organization (WHO) classifies neuroendocrine tumors according to the malignant potential of the tumor:
NETs of the GI tract and pancreas have their own staging systems based on the location and characteristics of the tumor. Some NETs use the staging system for other cancers. For example, the staging of a lung NET is the same as the staging of non-small cell lung cancer. These staging systems are created by the American Joint Committee on Cancer (AJCC).
Most NETs are found unexpectedly when people undergo testing for reasons unrelated to the tumor. Since NET tumors can be found in many locations in the body, diagnosing them requires a unique approach depending on the type of tumor, its location, whether it produces excess hormones, how aggressive it is and whether it has spread to other parts of the body.
At City of Hope, our cancer experts use a variety of tools and techniques for diagnosing neuroendocrine tumors, evaluating the disease and planning each patient’s individualized treatment. The diagnostic tests that may be used to diagnose NETs include:
Neuroendocrine tumor treatment options include:
Learn more about treatment options for neuroendocrine tumors
The clinicians at our GI Cancer Centers—located at each of our hospitals—are committed to offering state-of-the-art treatments for patients with neuroendocrine tumors. Our multidisciplinary team of board-certified medical oncologists, surgical oncologists, radiation oncologists and supportive care clinicians work with our patients to deliver quality clinical care with a patient-centered approach. After your diagnosis, your GI Cancer Center care team will discuss your options with you and help you develop a personalized care plan tailored to your individual needs.
When discussing treatment possibilities, they may also offer information on side effects for each option and how these may affect your quality of life. Because most NET patients are diagnosed at an advanced stage, an integrative approach is key to your well-being. Symptoms from the cancer or its treatment may include pain, gastrointestinal issues, high blood pressure and fatigue.
Your care team can also help you explore options for taking part in a clinical trial, which provides treatment as part of a research study. Clinical trials help determine whether a new treatment—including new drugs, different doses or a novel combination of treatments—may be better than the current standard approach for your type and stage of neuroendocrine cancer.
Supportive care therapies that may be recommended to help neuroendocrine cancer patients stay strong and maintain their quality of life include:
