Neuroendocrine tumor

A Neuroendocrine tumor (NET) is a neoplasm arising from the cells of the endocrine and nervous systems. These tumors often produce hormones, and depending on the type of hormone produced, can lead to various syndromes. NETs can be benign or malignant and can occur anywhere in the body, but are commonly found in the pancreas, lungs, and gastrointestinal tract.

Histopathology of a well-differentiated neuroendocrine tumor on a stomach biopsy

Classification

• NETs can be classified based on their site of origin, histological appearance, or behavior. The World Health Organization (WHO) classifies NETs into:
• Well-differentiated NETs: These are usually low-grade or intermediate-grade tumors that resemble normal cells.
• Poorly-differentiated Neuroendocrine Carcinomas (NECs): These are high-grade malignancies with an aggressive course.
• Mixed Neuroendocrine-Non-neuroendocrine Neoplasms (MiNEN): These tumors contain both neuroendocrine and non-neuroendocrine components.

Clinical Presentation

• The symptoms of a neuroendocrine tumor vary based on the location of the tumor and whether it is a functioning tumor (producing hormones) or non-functioning. Common symptoms include:
• Flushing
• Diarrhea
• Wheezing
• Weight loss
• Abdominal pain
• Skin rash

Diagnosis

• Diagnosis of NETs involves a combination of imaging, laboratory tests, and pathological assessment:
• Blood tests: To assess hormone levels, such as chromogranin A, and to gauge general health.
• Urine tests: To check for elevated hormone metabolites, such as 5-HIAA.
• Imaging studies: Including CT, MRI, and nuclear imaging like Gallium 68 PET scan to localize the tumor.
• Biopsy: A tissue sample is taken and assessed histologically to confirm the diagnosis.

Treatment

• Treatment of neuroendocrine tumors depends on the type, grade, and location of the tumor, as well as the patient’s health. Options include:
• Surgery: Used to remove the tumor. In some cases, such as early-stage pancreatic NETs, surgery can be curative.
• Chemotherapy and Radiation therapy: Often used for high-grade or metastatic tumors.
• Hormone therapy: Used to block excess hormone production in functioning tumors.
• Targeted therapy: Such as Everolimus or Sunitinib, used to target specific pathways in tumor cells.
• Peptide Receptor Radionuclide Therapy (PRRT): This is a targeted treatment approach that delivers radioactive material directly to the tumor cells.

Prognosis

The prognosis of NETs is variable and depends on factors such as tumor grade, stage, location, and the patient's general health. Well-differentiated tumors tend to have a better prognosis compared to poorly differentiated neuroendocrine carcinomas.

See Also

• Carcinoid
• Pancreatic neuroendocrine tumor
• Multiple endocrine neoplasia

References

• National Cancer Institute. (2023). Neuroendocrine Tumors. Retrieved from https://www.cancer.gov/types/neuroendocrine
• American Society of Clinical Oncology. (2023). Neuroendocrine Tumor: Types. Retrieved from https://www.cancer.net/cancer-types/neuroendocrine-tumor/types
• Mayo Clinic. (2023). Neuroendocrine tumors - Symptoms and causes. Retrieved from https://www.mayoclinic.org/diseases-conditions/neuroendocrine-tumors/symptoms-causes/syc-20354132
• Neuroendocrine Tumor Research Foundation. (2023). Diagnosing NETs. Retrieved from https://netrf.org/neuroendocrine-tumors/diagnosing-nets/

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