Neuroendocrine Tumor
Information about the symptoms, treatments, and prognosis of tumors that develop in cells responsible for producing hormones in response to neuronal stimuli.
Symptoms and Causes
Neuroendocrine tumors (NETs) result from the development of neoplasms, either malignant or benign, in cells that release hormones into the bloodstream in response to neuronal stimulation (neuroendocrine cells). These cells perform multiple functions, including the breakdown of food, regulation of blood pressure and heart rate, control of blood glucose levels, growth of the musculoskeletal system, and regulation of the rate at which food passes through the digestive tract or air and blood move through the lungs.
Two types of neuroendocrine tumors are distinguished according to their location:
- Gastroenteropancreatic (GEP) tumors:
- Pancreatic tumors: originate in the pancreas.
- Gastrointestinal tumors: develop anywhere in the digestive tract, although they are most commonly found in the jejunum or ileum, two sections of the small intestine.
- Non-gastroenteropancreatic tumors: develop outside the gastrointestinal tract or pancreas, most frequently in the lungs.
Neuroendocrine tumors are rare and, in most cases, malignant. Because they are often small and present with a wide range of symptoms that may be mistaken for other conditions, they can be difficult to diagnose. Prognosis is generally favorable, although it varies depending on the characteristics of the tumor. The estimated five-year survival rate is 90%.
Symptoms
Symptoms vary depending on the functional status of the tumor:
- Functioning tumors: produce substances, especially hormones, that cause specific symptoms.
- Intestinal tract tumors: cause carcinoid syndrome:
- Flushing of the skin of the face, neck, or upper chest.
- Telangiectasia: dilation and prominence of blood vessels.
- Shortness of breath.
- Diarrhea.
- Palpitations.
- Changes in blood pressure.
- Pancreatic tumors: affect the hormone-producing portion of the pancreas:
- Insulinoma: excess insulin production causes hypoglycemia, tremors, behavioral changes, and palpitations.
- Glucagonoma: increased glucagon production leads to diarrhea, skin lesions, diabetes, or thrombosis.
- Gastrinoma: excess gastrin production causes diarrhea and peptic ulcers.
- VIPoma: excessive vasoactive intestinal peptide (VIP) production results in watery diarrhea.
- Intestinal tract tumors: cause carcinoid syndrome:
- Non-functioning tumors: do not produce substances and therefore manifest through signs associated with the presence of a neoplasm:
- Localized pain.
- Fatigue.
- Nausea.
- Bleeding.
- Palpable mass.
- Jaundice, if located in the liver or bile ducts.
- Wheezing or shortness of breath, if located in the lungs.
- Constipation, diarrhea, or abdominal distension, if located in the intestine.
Causes
Neuroendocrine tumors develop as a result of mutations in the DNA of neuroendocrine cells, although the reasons why these mutations occur remain unknown.
Risk Factors
Risk factors that increase the likelihood of developing a neuroendocrine tumor are similar to those associated with other types of cancer. The most significant include:
- Smoking.
- Excessive alcohol consumption.
- Family history of cancer.
- Specific genetic syndromes:
- Neurofibromatosis type 1: mutation of the NF1 gene, which regulates cell growth and helps prevent tumor formation.
- Multiple endocrine neoplasia type 1 (MEN1): mutation of the MEN1 gene, which encodes the tumor suppressor protein menin.
- Von Hippel-Lindau syndrome (VHL): mutation of the VHL gene, which is involved in the regulation of cell division.
- Diabetes.
- Chronic pancreatitis.
- Tuberous sclerosis: causes benign tumors to develop in the skin, lungs, kidneys, or heart.
Complications
The most significant complication of neuroendocrine tumors is their spread to other organs. Metastasis commonly occurs in nearby lymph nodes, the liver, lungs, brain, or bones.
Prevention
There is no specific way to prevent the development of neuroendocrine tumors. Nevertheless, maintaining a healthy lifestyle is recommended to help prevent disease:
- Do not smoke.
- Limit alcohol consumption.
- Follow a balanced diet rich in fruits and vegetables.
- Exercise regularly.
- Maintain a healthy body weight.
Which specialist treats neuroendocrine tumors?
Neuroendocrine tumors are primarily managed within the specialty of Medical oncology. Specialists in Radiation oncology and Endocrinology and Nutrition are also frequently involved in patient care.
Diagnosis
The diagnosis of a neuroendocrine tumor requires several tests:
- Blood and urine tests: used to detect tumor markers as well as signs of abnormal hormone production.
- Physical examination: inspection and palpation may reveal abnormal masses or signs of hormonal imbalance.
- Imaging tests: magnetic resonance imaging (MRI) or computed tomography (CT) scans are used to visualize internal structures and identify physical changes or tumors.
- Functional imaging studies: positron emission tomography (PET) scans and scintigraphy allow assessment of both organ function and tumor activity.
- Biopsy: a tissue sample is obtained and examined in the laboratory to determine whether cancer cells are present. Findings may be classified into three categories:
- Low-grade neuroendocrine tumor: well differentiated, meaning the cells closely resemble normal cells and show a low proliferation index.
- Intermediate-grade neuroendocrine tumor: cancer cells are moderately similar to normal cells, with an intermediate proliferation index.
- High-grade neuroendocrine tumor: tumor cells are markedly different from normal cells and exhibit a high proliferation index.
Treatment
Treatment of neuroendocrine tumors requires a detailed evaluation of the characteristics and type of neoplasm in order to determine the most appropriate approach. The main treatment options include:
- Active surveillance: for low-grade tumors, regular follow-up assessments are scheduled to monitor growth, which is usually slow, while treatments aimed at symptom control are provided. The goal is to improve quality of life in patients who generally have a long life expectancy.
- Somatostatin analogs: used to control tumor growth and reduce hormone production.
- Radiotherapy: ionizing radiation is used to reduce the size of advanced tumors.
- Chemotherapy: anticancer drugs are administered to slow the growth of high-grade neoplasms.
- Surgery: surgical intervention is performed to remove localized tumor masses.
- Targeted therapy: medications directed against specific molecular pathways involved in the disease are used. Commonly employed agents include proton pump inhibitors, calcium channel blockers, and glucocorticoids.
