A group of rare tumors that begin to develop in specialized cells of the neuroendocrine system is called neuroendocrine tumors (NETs). In most cases, they appear in the GI (gastrointestinal) tract, lungs, and pancreas. The only way to improve life expectancy is early diagnosis and proper treatment.
However, the neuroendocrine cells combine traits of nerve cells and hormone-producing endocrine cells. Moreover, most diagnosed neuroendocrine tumors are malignant (cancerous). In general, there are multiple types of neuroendocrine tumors, and some of them are easily mistaken for less serious conditions. The primary characteristics of NETs are how fast they are growing and the symptoms a person experiences.
These tumors affect about 6 in 100,000 people in the whole world. While anyone may develop these tumors, they are usually diagnosed in people between the ages of 50 and 60.
Types of Neuroendocrine Tumors
Healthcare providers have divided these tumors based on whether they release hormones. For example, functional NETs release hormones that may cause hormone-related symptoms, and non-functional NETs that do not release hormones, but may cause symptoms if they affect an organ. Check some types of neuroendocrine tumors below:
- Gastrointestinal neuroendocrine tumors (GI-NETs) – Most diagnosed tumors are located in the gastrointestinal tract. While some of them start in the intestines, others may develop in the rectum or appendix. Sometimes, these tumors are called carcinoid tumors.
- Lung neuroendocrine tumors – These tumors begin to develop in the lungs or bronchi (the tubes that carry air from the windpipe to the lungs). Moreover, this type of neuroendocrine tumor is the second most common form of these tumors.
- Pancreatic neuroendocrine tumors (P-NETs) – In such cases, the tumor develops in the pancreas, and it is considered a form of pancreatic cancer.
However, these tumors may also develop in other parts of the body, but it is less common. For example:
- Parathyroid glands
- Adrenal glands
- Thymus
- Thyroid gland
- Pituitary gland
Symptoms
In most cases, these tumors do not cause symptoms until they affect an organ. Check some symptoms often experienced by people with NETs below:
- Extreme tiredness (fatigue)
- Nausea
- Vomiting
- Diarrhea
- Stomach pain
- Dyspnea (shortness of breath)
- Cough
It is important to understand that if you have the previous symptoms, it does not necessarily mean you have a neuroendocrine tumor. In any case, it is advised to see a doctor for a diagnosis and treatment.
Causes and Risk Factors
In general, experts do not fully understand what exactly causes the development of these tumors. However, they appear like other types of cancer when specific cells develop DNA mutations (changes). DNA holds instructions that tell cells when to grow, multiply, and die, but a mutated DNA gives the cells different instructions that make them grow and multiply abnormally. If these abnormal cells become too numerous, they form a mass called a tumor. In advanced stages of the cancer, this tumor may break and spread to other parts of the body (such as the bones, lungs, or others).
In addition, physicians have identified some factors that could increase your risk of developing neuroendocrine tumors. Examples include:
- Multiple endocrine neoplasia (MEN) – This disorder causes overactive tumors to develop in different organs and endocrine system glands. The most common cancer syndrome associated with NETs is MEN1 (type 1). Usually, it is common in people with pancreatic NETs (P-NETs).
- Von Hippel-Lindau syndrome – This is a genetic disorder that increases the risk of benign (noncancerous) and malignant (cancerous) tumors in multiple parts of the body.
- Neurofibromatosis type 1 – It is a health condition that causes tumors to grow on the skin and nerves. These tumors may affect your eyes as well as other parts of the body.
- Tuberous sclerosis complex – It is a serious health condition that may cause benign (noncancerous) tumors to grow anywhere on the body (in most cases, in the brain).
- Cowden syndrome – This is also a genetic disorder that may cause benign growths that significantly increase the risk of some types of cancer.
What Happens if Neuroendocrine Tumors are Left Untreated?
Those who develop neuroendocrine tumors may also experience some complications, especially if they are left untreated. Check some complications below:
- Carcinoid syndrome – This complication may also cause flushing, diarrhea, wheezing, and heart problems.
- Specific syndromes similar to low blood sugar (hypoglycemia)
- Carcinoid heart disease – This is a serious complication of a neuroendocrine tumor that negatively affects the heart valves. Sometimes, it may cause heart failure.
- Hyperglycemia
- Cushing’s syndrome – This genetic condition may also cause hypertension (high blood pressure), hyperglycemia (high blood sugar), and weight changes.
- Bowel obstruction – This complication may cause severe abdominal (belly) pain, bloating, constipation, nausea, and vomiting.
- Peptic ulcers – For example, Zollinger-Ellison syndrome, which causes severe stomach ulcers.
- Liver damage/metastasis – In some cases, cancerous tumors may spread to the liver and cause jaundice (yellowing of the eyes and skin).
- Nutritional Deficiencies – This complication often occurs due to malabsorption or poor diets.
- Anxiety disorders
The previous list does not contain all possible complications of neuroendocrine tumors. In any case, you can consult with your doctor about ways to reduce the risk or even prevent them. In addition, it is not possible to prevent these tumors because doctors do not fully understand what exactly causes them.
Diagnosis
Sometimes, it is difficult to diagnose a neuroendocrine tumor because the symptoms it causes are very similar to other, less serious health conditions. However, to confirm or rule out this condition, doctors often perform the following tests and procedures. For example:
- Biochemical tests – These tests are used to measure the amount or activity of certain enzymes or proteins in the blood and urine. They may also show signs of a functional NET.
- Imaging tests – The following tests are used to get detailed images of different structures and organs in the body. They may show the exact location and size of the tumor. Usually, physicians perform a CT (computerized tomography) scan, an MRI (magnetic resonance imaging) scan, or X-rays. In some cases, doctors may also perform a PET (positron emission tomography) to see whether the cancer has spread.
- Endoscopy – This procedure involves a thin and flexible tube with a lighted camera on the end (endoscope). It helps detect the tumor.
- Endoscopic ultrasound – This procedure combines an endoscopy with an imaging test that uses sound waves (ultrasound). It usually helps diagnose a neuroendocrine tumor in the pancreas.
- Biopsy – This test involves the removal of a small amount of the tumor for testing. Doctors will examine it under a microscope to check for cancerous cells.
Once you are diagnosed with a neuroendocrine tumor, doctors may perform additional imaging tests to determine the stage (extent) of the cancer. It helps make the best treatment plan for you.
Treatment
While the primary treatment is surgery to remove the tumor, doctors may recommend other treatments to destroy cancerous cells. Check some examples below:
- Somatostatin analogs – This treatment involves specific medicines used to prevent the body from producing too many hormones. It helps relieve the symptoms caused by NETs.
- Chemotherapy – This treatment uses strong medicines to kill cancerous cells throughout the body. Sometimes, it can be used to shrink a large tumor before surgery.
- Targeted therapy – This therapy involves specific medicines that block a protein in the cancerous cells, causing them to die.
- Radiation therapy – Doctors often recommend a type of radiation therapy for people with neuroendocrine tumors. It is called peptide receptor radionuclide therapy (PRRT), and it delivers small amounts of radioactive substances to the NETs that release hormones.
Frequently Asked Questions
Can a neuroendocrine tumor be cured?
These tumors can be treated if they are found in the early stages. They are removed with surgery. The problem is that these tumors are slow-growing and are often found in advanced stages. In this case, doctors usually prescribe treatments to ease the symptoms and slow the growth of the tumor.
When should I go to the emergency room (ER)?
Call 911 or go to the nearest emergency room (ER) if you experience swelling (edema) because it may indicate heart failure or sudden breathing problems. Otherwise, it may lead to permanent damage to certain organs or even death.
What is the life expectancy of a neuroendocrine tumor?
Generally, the life expectancy varies widely among people with neuroendocrine tumors because it depends on the location, stage, and type of the tumor. For instance, the 5-year survival rate for people with localized NETs is about 90%, but if the tumor spreads to other parts of the body, the same survival rate may decrease to 57%. Ask your healthcare provider if you have any other questions.
