Neuroendocrine tumors (NET)
What are neuroendocrine tumors?
Neuroendocrine tumors (NET) develop mainly in the gastrointestinal tract and respiratory tract. They originate in neuroendocrine cells, which are characterized by the ability to receive nerve transmission and the ability to secrete hormones.
The cell from which the tumor develops can be similar to the normal cell that functions in the body, and is then referred to as "differentiated", meaning one that has undergone cell sorting. Differentiated tumors tend to grow at a slow rate, so they pose a lower risk compared to poorly differentiated tumors which are rarer and more aggressive.
The types of neuroendocrine tumors depend, among other things, on where they develop and on the effect of the hormone (or other substance) secreted from them.
Neuroendocrine tumors are commonly classified as non-functioning NET tumors, which do not secrete hormones that cause symptoms, and functioning NET tumors, which produce hormones that cause various symptoms.
What is the prevalence of neuroendocrine tumors?
A 2012 study published in the United States reported about 7 patients per 100,000 people per year. This is a 6.4-fold increase over previous decades. One explanation for this may be the improvement in test sensitivity.
What are the symptoms?
The symptoms that appear in patients with functional tumors that produce hormones depend on the type of hormone. For example, a tumor that secretes insulin will cause low glucose (sugar) levels in the blood and related symptoms – sweating, tremors, loss of consciousness. A tumor that secretes gastrin will result in the secretion of excessive acid in the stomach and recurrent ulcers in the stomach. A tumor that secretes serotonin will trigger flushing and diarrhea attacks (carcinoid syndrome).
Sometimes, the symptoms do not stem from a hormone secreted by the tumor, but from the tumor itself that presses on nearby organs, from the involvement of blood vessels or nerves, from a bowel obstruction and more.