What Is Neuroendocrine Cancer?

Neuroendocrine cancers are growths that develop when hormone-producing cells of the body start to multiply out of control. These cells form tumors that can release hormones that cause various symptoms.

Hormones are the body's chemical messengers. They send signals from one cell to another through the bloodstream. These chemicals can have a variety of effects throughout the body. Often, they regulate the body's basic processes, including growth, development, and metabolism.

The neuroendocrine system includes nerves, glands, and other tissues that work together to produce hormones. Neuroendocrine cancers are diverse tumors forming in many different parts of the body. These cancers have varying causes, symptoms, and prognoses.

This article will review types of neuroendocrine cancer, their general symptoms, how they are diagnosed and treated, and the general prognosis for someone diagnosed with neuroendocrine cancer. 

Types of Neuroendocrine Cancer

Neuroendocrine tumors are often slow-growing. They are neuroendocrine cancer if they grow quickly and spread from the original site. This spread makes the tumor malignant, which means it’s cancer. 

Many types of tumors and cancers develop in the neuroendocrine system, in many parts of the body.

Some examples are:

• Gastrointestinal and lung cancers: Neuroendocrine cancers called carcinoid tumors can form in the gastrointestinal system or, very rarely, the lungs. These rare cancers develop primarily in adults. About 8,000 gastrointestinal carcinoid tumors are diagnosed each year in the United States.
• Pancreatic cancer: Pancreatic neuroendocrine tumors (PNETs) are also called islet cell tumors. These cancers form in the pancreas, making up about 7% of all pancreatic cancers. There are about 4,300 cases in the United States a year.
• Thyroid cancer: Medullary thyroid cancers make up about 3% to 4% of thyroid cancers, with about 1,000 cases in the United States annually.
• Adrenal cancer: Called pheochromocytoma, these are rare tumors that develop on the adrenal gland on top of the kidney. These tumors are often noncancerous, but about 15% are malignant and spread to other body parts. Pheochromocytomas are rare, but they may be more common than previously thought. They often go undiagnosed. Pheochromocytomas outside the adrenal glands are called paragangliomas and are very rare.
• Skin cancer: Merkel cell cancer (also called neuroendocrine carcinoma of the skin) is a rare type of skin cancer that develops in areas of the skin exposed to the sun. Only about 2,000 cases are reported in the United States each year.
• Lung cancers: Two types of neuroendocrine tumors can start in the lungs. Small cell lung cancer, also called oat cell lung cancer makes up 10% to 15% of lung cancers. There are about 30,000 cases in the United States annually. Large cell neuroendocrine carcinoma is a rare type of lung cancer. It is fast-growing and very similar to small-cell lung cancer. It makes up about 1% to 2% of lung cancers, with approximately 2,000 to 4,500 Americans getting this cancer each year.

Neuroendocrine Cancer Symptoms

Symptoms of neuroendocrine cancers are based on the type of tumor, where it is located in the body, and what hormones it releases. 

In rare cases, carcinoid tumors (wherever they are located) can release hormones and cause carcinoid syndrome. Symptoms of carcinoid syndrome include feeling flushed, nausea, vomiting, and diarrhea.

Pancreatic neuroendocrine tumors can make too much of certain hormones, impacting the gastrointestinal system and the rest of the body.

• PNETs that make a hormone called gastrin can cause Zollinger-Ellison syndrome: Symptoms include stomach ulcers (pain, nausea, and loss of appetite) and bleeding leading to anemia (feeling tired and short of breath). 
• PNETs can make glucagon, which raises blood sugar. Symptoms are mild and include feeling thirsty or hungry and having to pee a lot. People with PNETs may develop necrolytic migratory erythema, a red rash with swelling and blisters that move around on the skin.
• PNETs that make insulin lower blood sugar. Symptoms include weakness, confusion, sweating, and a rapid heartbeat. 
• PNETs that make somatostatin can cause digestive issues, symptoms of diabetes, and jaundice (yellowing of the skin and eyes).
• PNETs that make vasoactive intestinal peptides can cause diarrhea that starts mild but gets worse over time, as well as other digestive symptoms and flushing.

Medullary thyroid cancer may develop as a lump in the throat, causing hoarseness or making it hard to breathe.

Adrenal pheochromocytomas are most often noncancerous tumors, but they can become cancer. Pheochromocytomas may cause symptoms like high blood pressure, headaches, irregular heartbeat, and sweating.

Merkel cell tumors are firm, pink, red, or purple lumps or bumps. They don’t usually hurt but can grow fast and sometimes turn into open sores.

People with neuroendocrine lung tumors may cough, wheeze, develop pneumonia (a lung infection), or have chest pain.

People with neuroendocrine cancer may also have more general cancer symptoms, including:

• Fatigue
• Loss of appetite
• Unexplained weight loss

Causes and Risk Factors

There are a variety of causes of neuroendocrine cancers. The cause of most neuroendocrine cancers is unknown, and there are no known avoidable risk factors for these tumors. One neuroendocrine cancer that bucks the trend is small cell lung cancer. Its risk factors include exposure to tobacco smoke.

Factors that increase a person’s risk for neuroendocrine cancer include:

• Their race or ethnicity: Neuroendocrine cancers are more commonly diagnosed in White people.
• Their gender: Neuroendocrine cancers are slightly more common in women.

Note that Verywell Health prefers to use inclusive terminology. But when citing health authorities or research, the terms for gender or sex from those sources are used.

Other medical conditions could increase a person’s risk of developing neuroendocrine tumors. For instance, certain digestive diseases that damage the stomach and reduce acid production may increase the risk of gastrointestinal carcinoid tumors.

Risk factors for Merkel cell cancers include infection with Merkel cell polyomavirus (MCV), a common virus, but not much is known about it or how it’s linked to this cancer. Ultraviolet (UV) light (from the sun, tanning beds, or skin condition treatment) is also a common risk factor for Merkel cell cancers.

Genetic conditions sometimes cause neuroendocrine cancers. These include:

• Von Hippel-Lindau syndrome leads to tumors throughout the body.
• Neurofibromatosis type 1 causes tumors around nerves.
• Multiple endocrine neoplasia syndromes cause tumors in more than one endocrine gland at a time.
• Hyperparathyroid-jaw tumor syndrome leads to tumors in the parathyroid gland.
• Paraganglioma-pheochromocytoma syndrome can lead to pheochromocytoma.

Diagnosis

The tests a healthcare provider uses to diagnose neuroendocrine cancer will vary by the type of cancer.

These tests will include taking a detailed personal and family medical history. They will likely also have imaging studies done to see inside the body and blood tests to see if the body’s hormones are high or low.

The healthcare provider may also want to take a sample of the tissue, called a biopsy, to have it examined under the microscope. This will help them understand if the tumor is cancer and how to treat it.

A healthcare provider may use an endoscope to visualize or biopsy carcinoid cancer in the upper intestinal tract and pancreas. An endoscope is a flexible tube with a light, camera, and tools. It is inserted through the throat.

Tumors in the colon or rectum may require a colonoscopy, in which a flexible tube with a camera is inserted through the rectum to view the lower digestive system.

They may test for related genetic conditions that may cause neuroendocrine tumors.

Treatment

Typically, neuroendocrine cancers are treated with surgery, radiation, and chemotherapy. Some people may also be candidates for treatment with targeted therapy (aimed at specific aspects of the tumor cells) or immunotherapy (which uses the immune system to attack the tumor).

Symptoms of neuroendocrine cancers caused by hormone imbalances may be treated with other drugs. Somatostatin drugs such as Sandostatin (octreotide) may help shrink some neuroendocrine tumors and are often used as a treatment for carcinoid tumors.

Some slow-growing neuroendocrine cancers may be curable. A person with neuroendocrine cancer can enter remission if the tumor is cleanly removed with surgery and hasn’t spread to other body parts.

Prognosis 

Your individual prognosis is based on many factors, including the size of the tumor, how much it has spread, what hormones it is making, where it is located, and if the cancer can be removed with surgery. 

Survival rates for neuroendocrine cancer vary by type of cancer and whether it has spread. These are averages and cannot predict the course of an individual's cancer journey. Some neuroendocrine cancers are severe, mainly if they’ve already spread when discovered.

Survival and prognosis statistics include:

• The prognosis for carcinoid cancer is generally good if entirely removed by surgery. If cancer has spread, the prognosis is less favorable.
• Pancreatic neuroendocrine tumors are severe, with a five-year survival rate of 53%.
• The outlook for medullary thyroid cancer is good, with a five-year survival rate of 89%.
• Adrenal pheochromocytomas that haven’t spread have an excellent five-year survival rate of 95%. If they have spread or returned, the five-year survival rate is between 34% and 60%.
• Merkel cell cancer is severe and has an average five-year survival rate of 64%.
• Small cell lung cancer is severe. Only 7% of people diagnosed with small cell lung cancer live five years after diagnosis. Survival is slightly better for small cell lung cancers found early, at 27%.
• The five-year survival rate for a lung NET is 89%, but there’s a high risk of recurrence after successful treatment.

Coping

A diagnosis of neuroendocrine cancer can be very upsetting. The tumor may be causing unwelcome symptoms, and treatments can have side effects or cause changes to your body and how you feel. Bring your questions to your treatment team so you understand your treatment options and what to expect.

While processing your diagnosis and going through treatment, lean on your family, friends, and local community for emotional and physical support. In-person or online support groups may be useful at this time, as they have faced a similar challenge and can offer advice and camaraderie.

If you’re experiencing sadness, anxiety, or anger, know this is normal. Ask your care team for access to a mental health professional or counselor to help you cope with the emotional and social effects of having neuroendocrine cancer.

Summary

Neuroendocrine cancers develop in cells that make hormones. These cells grow out of control. They can spread to other body parts.

These cancers make hormones, which can cause many symptoms. Hormones control the body’s basic processes. These include growth, development, and metabolism.

Neuroendocrine tumors develop in many parts of the body—most commonly in the intestines, lungs, and pancreas. Healthcare providers often can’t find a cause for these cancers. Some genetic diseases cause them. 

Treatment for neuroendocrine cancers varies. It can include surgery, radiation, chemotherapy, targeted therapy, and immunotherapy. The outlook for a person with a neuroendocrine tumor changes. Some neuroendocrine tumors are severe.

A Word From Verywell

Neuroendocrine cancers are a large group with varying symptoms, treatment options, and prognoses. Your outlook is based on many factors, including the size of the tumor, how much it has spread, what hormones it is making, where it is located, and if cancer can be removed with surgery. 

Ask your healthcare provider for more information on your specific cancer. Seek out the company of others with your cancer for support.