An Introduction To Neuroendocrine Tumors And Types

Neuroendocrine tumors

What are Neuroendocrine Cells?

Neuroendocrine cells are present all over the body such as the skin, stomach, pancreas, kidneys, thyroid and the intestines. In normal, healthy individuals, a variety of stimuli cause the neurons (nerve cells) to convey neurotransmitters (chemicals which are responsible for transmitting nerve impulses) to these neuroendocrine cells, which in turn release hormones into the blood.

In short, the neuroendocrine cells are responsible for the release of hormones into the blood. In this way, the central nervous system plays a pivotal role in normal functioning of and release of hormones from our endocrine glands.

Example: The thyroid gland, on receiving signals from the brain, releases the thyroid hormones. Therefore, neuroendocrine tumors are cancerous growths which begin inside the neuroendocrine cells.

Epidemiology: A study conducted in Bombay Hospital from the year 2000-2007 shows that the age of developing NETs was around 41 to 60 years with a significantly higher incidence in males than in females and a higher incidence of stomach involvement.

Who Are At Risk For Developing Neuroendocrine Tumors?

  • Patients inheriting the MEN1 (Multiple Endocrine Neoplasia Type 1) and VHL (Von Hippel-Lindau Syndrome) are at a higher risk of developing neuroendocrine tumors.
  • Patients who present with a family history.
  • Tobacco smoking
  • Men are more likely to develop neuroendocrine tumors as compared to women.
  • Immuno-compromised patients, which is patients having HIV.
  • Prolonged exposures to the sun and arsenic have a higher risk of developing neuroendocrine tumors.

Survival rate: Patients diagnosed with neuroendocrine tumors have a 5 year survival, depending upon the type of neuroendocrine tumor.

What Are The Types of Neuroendocrine Tumors?

Based on the type of growth, the tumors can be Benign or Malignant.

Benign tumors are harmless and can be differentiated from the normal tissue. These do not spread to other parts and can be easily removed from the affected part.

Malignant tumors spread to other parts. They cannot be easily differentiated from the normal tissues and since the spread is haphazard, they cannot be removed if they affect vital organs.

Based on the Organs or Parts Affected, Neuroendocrine Tumors have the Following Types:

  1. Gastrointestinal Neuroendocrine Tumors (GI NETs): Tumors affected the gastrointestinal tract can occur anywhere from the esophagus and stomach to the large and small intestine and appendix.
  2. Pulmonary Neuroendocrine Tumors (Pulmonary NETs): This type of neuroendocrine tumor was previously known as Carcinoid tumors. These pertain to the lungs. Majority of these tend to grow aggressively and spread rapidly.
  3. Pancreatic Neuroendocrine Tumors (pNETs): When the tumor affects the pancreas, the tumor cells mimic the islet cells.
  4. Merkel Cell Carcinoma: It is a type of cancer affecting the hormone producing cells below the skin and hair follicles. These are seen in 60% of patients with neuroendocrine tumors.
  5. Medullary carcinoma of Thyroid
  6. Pheochromocytoma: This is a rare type of cancer which affects the chromaffin cells of the adrenal glands. It commonly affects the adrenal medulla. This type of tumor increases the production of adrenalin and noradrenalin.

Staging of neuroendocrine tumors is done based on the organ or part affected. There is no specific gradation technique applied to neuroendocrine tumors specifically.

Diagnosis of neuroendocrine tumor cells can be done on the basis of sign and symptoms, MRI, CT or PET-CT scans followed by Biopsy. Molecular testing of these tumors can be done to assess the type of tumor and treatment options.

Recent research and development studies have suggested that drugs such as Leucovorin, Oxaliplatin, and Octreotide can either destroy the tumor cells or slow down the growth and multiplication of the neuroendocrine tumor cells.

Reviewed By:

Dr. Kaushal M. Bhavsar (MBBS, MD)

Assistant Professor in Pulmonary Medicine, GMERS Medical College, Ahmedabad