How Do Neuroendocrine Tumors Spread & How Does The Neuroendocrine System Respond To Stress?

Neuroendocrine tumors are a very rare type of tumor. This type of tumor originates from special body cells that are known as neuroendocrine cells. The neuroendocrine cells have the characteristics of both the neural or nerve cells as well as those of the hormone-producing cells. The hormone-producing cells secrete hormones in the blood when signaled by the central nervous system. The neuroendocrine tumors are capable of releasing hormones into the blood as they contain hormone-producing cells. These tumors have no fixed location of occurrence in the body so they can be seen anywhere. Although the most common sites where this tumor is seen are lungs, appendix, pancreas, rectum or the gastrointestinal system. ⁽¹⁾

How Do Neuroendocrine Tumors Spread?

Cancer cells can spread from the organ in which it had been originated to a different organ of the body. This process of spreading cancer cells from one organ to another is called metastasis. The doctor can change the treatment plan if there is a metastasis of the cancer cells. The neuroendocrine tumors can also spread to other organs of the body like: bone, lungs, liver, lymph nodes of the part where cancer originated (regional lymph nodal involvement), pancreas, bones and the tissues or organs that are located near the organ in which cancer had originated for example pleura, fat tissue or the peritoneum.

How Does The Neuroendocrine System Respond To Stress?

When there is exposure to stress, the normal homeostasis of the body gets disturbed. Due to this, there is activation of two systems in the body. These two systems are the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. When these two systems are activated, there is alteration in the action of endocrine and neural systems as well. These alterations or adaptation to stress is known as stress cascade or stress response. The changes occurring in the homeostasis of the body leads to certain demands of the body. These demands of the body are met with the help of certain metabolic and physiological changes in the body. These metabolic and physiological changes are made by the stress cascade.

Exposure to stress leads to the release of a hormone from the hypothalamus named corticotropin-releasing hormone (CRH) and this leads to the release of adrenocorticotropin hormone (ACTH). These hormones are released into the circulation. Then ACTH acts on the adrenal cortex, which in turn releases glucocorticoids.

Glucocorticoids then act to stop the release of CRH through a negative feedback mechanism. Imbalance in the CRH can lead to diseases like Cushing’s and Addison’s disease. This way glucocorticoids work to maintain the levels of CRH in the blood during stress.

NETs are the tumors that originate in the neuroendocrine system of the body. NETs are classified on the basis of their organ of origin.

Gastrointestinal Neuroendocrine Tumors (GI NETs): GI NETs are common types of neuroendocrine tumors. These tumors originate in the organs of a gastrointestinal system like stomach, rectum, small intestine, colon, appendix, and esophagus. Most of the GI NETs originate from the small intestine and these tumors release a hormone named serotonin. When serotonin is released in excess amounts, it leads to carcinoid syndrome.

Lung Neuroendocrine Tumors (Lung NETs): Lung NETs are also quite a common type of NETs. They have their origin in the lungs and most often in the bifurcation of the windpipe that gives way towards the lungs. Lung NETs have four subtypes- typical carcinoid tumors, atypical carcinoid tumors, large cell lung neuroendocrine carcinomas and small cell lung neuroendocrine carcinomas.

Pancreatic Neuroendocrine Tumors (pNETs): Pancreatic NETs are similar to islet cells that are seen in the pancreas in appearance. There are different types of pancreatic NETs based on the type of hormones produced by the tumors like glucagonoma, insulinoma, gastrinoma, somatostatinoma, etc.

Others:

Parathyroid cancer
Thymic neuroendocrine cancer
Pheochromocytoma
Pituitary gland tumors
Medullary carcinoma of the thyroid ^{(2), (3)}

Conclusion

When the NETs spread from the organ of origin to another organ, this process is known as metastasis. Cancer can spread to organs like the liver, lungs, lymph nodes present near the organ with tumors and bones. When there is exposure to stress, the normal homeostasis of the body gets disturbed. This disturbance is brought to normal with the help of the neuroendocrine system of the body that releases hormones.

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How Do Neuroendocrine Tumors Spread & How Does The Neuroendocrine System Respond To Stress?