• By Jrsh Admin
• In Health and Tips,
• Posted December 26, 2024

Neuroendocrine Tumors: Types, Symptoms, Risk Factors & Treatment

Overview

Neuroendocrine tumors (NETs) are rare slow-growing cancers that arise in neuroendocrine cells throughout the body, including in the lungs, gastrointestinal tract, and pancreas. 

They can be classified into functional (hormone-producing) or nonfunctional (non-hormone-producing) types, and include carcinoid tumors, pancreatic NETs, and pheochromocytomas. Symptoms will depend on the location of the tumor and the hormones secreted but may include abdominal pain, flushing, diarrhea, or unexplained weight loss. 

Risk factors for NETs include genetic syndromes such as MEN1 syndrome, family history of NETs, and predisposing diseases. Surgical intervention, hormone therapy, targeted drugs, chemotherapy, and peptide receptor radionuclide therapy (PRRT) may be appropriate depending on the type and stage of the tumor. Early diagnosis results in good outcomes.

Types of  Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are classified according to their location, functionality, and the types of hormones they produce. The following are the main types:

1.  Carcinoid Tumors

• These tumors are located in the gastrointestinal tract, including the stomach, small intestine, colon, and rectum or in the lungs.
• In some cases, they may secrete serotonin and other chemicals that cause carcinoid syndrome.

2.    Pancreatic Neuroendocrine Tumors (PanNETs)

• They develop in the pancreas and may be functional or non-functional.
• Functional PanNETs include; insulinomas, gastrinomas, glucagonomas, somatostatinomas and VIPomas named after hormones secreted.

3.   Pheochromocytomas and Paragangliomas

• Pheochromocytomas arises from the adrenal glands
• Paragangliomas arises outside the adrenal gland but in similar nerve cells
• Both can produce hormones that are related to adrenaline leading to high blood pressure, sweating and palpitation.

4.  Medullary Thyroid Carcinoma

• This is a form of thyroid cancer arising from the C cells that produce calcitonin.

5.  Merkel Cell Carcinoma

• It is an aggressive type of skin cancer arising from neuroendocrine cells on the skin.

6.  Gastrointestinal Stromal Tumors (GISTs)

• Although not technically NETs, they are sometimes categorized as such because of their origin from the gastrointestinal tract.

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Symptoms of neuroendocrine tumors

The symptoms of NETs are variable, depending on the site and the hormone secreted; however, they may present with:

• Gastrointestinal symptoms: Abdominal pain, diarrhea, or nausea.
• Hormonal effects: Flushing, sweating, or alterations in blood sugar.
• General signs: Fatigue, weight loss, or changes in appetite.
• Specific symptoms: Hypertension, palpitations (pheochromocytomas), or skin changes (Merkel cell carcinoma).
• Many symptoms are non-specific and thus pose a challenge for early diagnosis.

Causes of neuroendocrine tumors

The causes of NETs are not clearly known, but they have been linked to some genetic and environmental factors, such as:

• Genetic Mutations: Changes in DNA can cause cells to grow uncontrollably, leading to NETs.
•  Inherited Conditions: Genetic syndromes like Multiple Endocrine Neoplasia type 1 (MEN1), Von Hippel-Lindau syndrome, or Tuberous Sclerosis increase risk.
• Family History: A family history of NETs or related syndromes raises susceptibility.
• Chronic Inflammation: Possibly prolonged inflammation of the gut or pancreas.
•  Environmental Factors: Indeterminate though environmental exposures of some nature could be causal.

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Diagnosis of neuroendocrine tumors

The diagnosis of neuroendocrine tumors (NETs) is done with a combination of clinical assessment, imaging studies, and laboratory tests to confirm the presence, type, and extent of the tumor. The most important steps are:

1.  Medical History and Physical Examination

• Evaluate symptoms, family history, and risk factors.

2.  Biochemical Tests

• Measure levels of hormones, for example, serotonin, chromogranin A, insulin.
• Urine tests for metabolites such as 5-HIAA (5-hydroxyindoleacetic acid).

3. Imaging Studies

• CT/MRI scans: detect and localize tumors.
• PET scans: detect metastasis and sites of active tumor.
• Octreotide scans (SRS) or Gallium-68 DOTATATE PET/CT: Specialized imaging for somatostatin receptor-positive NETs.

4.  Biopsy

• Tissue sampling confirms the diagnosis and tumor grade (well-differentiated or poorly differentiated).

5.  Endoscopic Procedures

• Endoscopy or colonoscopy for gastrointestinal NETs.
• Bronchoscopy for lung NETs.

Risk Factors of neuroendocrine tumors

The risk factors for NETs include:

• Genetic Syndromes: Inherited conditions such as MEN1, Von Hippel-Lindau syndrome, and Tuberous Sclerosis increase susceptibility.
• Family History: Having a family history of NETs or associated genetic disorders raises the risk.
•  Age: NETs are more common in middle-aged and older adults, though they can occur at any age.
• Sex: Some types of NETs have a mild gender preference. For example, carcinoid tumors are more common in females.
• Chronic Conditions: Diseases or conditions such as atrophic gastritis or Zollinger-Ellison syndrome can increase susceptibility to developing NETs.
• Lifestyle Factors: Though not exclusively, smoking, alcohol, and toxin exposure may also increase the chances of having a NET.

When to see a doctor

You should consult a doctor if you have persistent or unusual symptoms that may be related to a neuroendocrine tumor (NET), such as:

• Unexplained Symptoms: Persistent abdominal pain, diarrhea, nausea, or flushing.
• Hormonal Imbalances: Sudden changes in blood sugar, blood pressure, or heart rate.
• Weight Changes: Unexplained weight loss or gain.
• Fatigue: Prolonged tiredness without a clear cause.
• Skin Changes: Lumps, discoloration, or rapidly growing nodules (e.g., Merkel cell carcinoma).

Treatment of neuroendocrine tumors

The treatment of NETs varies with the type, size, location, functionality, and stage of the tumor. Some common treatments include:

1.   Surgery:

• Curative: removal of the tumor, whenever possible.
• Debulking: partial removal of the tumor to reduce symptoms or make other treatments more effective.

2.   Medications:

• Somatostatin Analogues: drugs such as octreotide or lanreotide to control hormone-related symptoms and slow tumor growth.
• Targeted Therapy: drugs such as everolimus or sunitinib that block specific pathways involved in tumor growth.
• Chemotherapy: for high-grade or aggressive NETs.

3.    Peptide Receptor Radionuclide Therapy (PRRT):

• Targeted therapy wherein the radiation is delivered straight to the tumor cells expressing somatostatin receptors.

4.   Radiation Therapy

•  Localized tumors or to ease symptoms in the advanced stage

5.   Hormonal Therapy

• To alleviate symptoms produced by excess production of a hormone

6.   Supportive Care

• Treatment of symptoms, such as pain, diarrhea, or flushing with appropriate medicines.

Tags

• Neuroendocrine Tumors
• Risk Factors of neuroendocrine tumors
• Diagnosis of neuroendocrine tumors
• Causes of neuroendocrine tumors