Neuroendocrine tumors (NETs) are a group of rare neoplasms that originate in the specialized neuroendocrine cells found throughout the body. These cells have both nerve cell (neuro) and hormone-producing (endocrine) characteristics. NETs can occur in various organs, most commonly in the gastrointestinal tract and the lungs, but they can also develop in other areas such as the pancreas, thyroid, and adrenal glands.
Most NETs take years to develop and grow slowly. However, some NETs can be fast-growing.
NETs are classified into different types based on the specific organ they originate from. The most common types include:
Gastrointestinal (GI) tract. NETs develop most commonly in the GI tract, specifically in the large intestine (20%), small intestine (19%), and appendix (4%). GI tract NETs used to be called carcinoid tumors.
Lung. The lung is the second most common location of NETs. About 30% of NETs occur in the bronchial system. Lung NETs also used to be called carcinoid tumors.
Pancreas. Approximately 7% of NETs can develop in the pancreas. Pancreas NETs used to be called islet cell tumors.
NETs can also begin in other organs. In about 15% of cases, a primary site cannot be found.
Sometimes, NETs may develop in or on the adrenal glands. These rare types of NETs are called pheochromocytoma and paraganglioma.
Other types of tumors that begin in hormone-producing cells including thyroid cancer, adrenal gland tumors, and pituitary gland tumors.
The symptoms of NETs can vary widely depending on the tumor’s location and whether it produces hormones. Some common symptoms include abdominal pain, diarrhea, flushing, wheezing, and weight loss. Hormone-producing NETs can cause unique symptoms related to hormone overproduction.
Diagnosis typically involves a combination of imaging studies, such as CT scans, MRI, and endoscopy, as well as blood tests to measure hormone levels. Biopsy is often necessary to confirm the diagnosis.
Grading and Staging:
NETs are typically graded as low, intermediate, or high grade based on their aggressiveness. Staging is determined by the size of the tumor, the extent of spread, and whether nearby lymph nodes are involved.
Treatment options for NETs depend on the type, stage, and location of the tumor. Treatment may include surgery, chemotherapy, targeted therapies, radiation therapy, and somatostatin analogs to control hormone production. In some cases, a combination of these treatments may be used.
The prognosis for NETs varies widely depending on the specific type and stage of the tumor. Some NETs are slow-growing and may have a good prognosis, while others can be more aggressive. Early diagnosis and appropriate treatment can significantly impact outcomes.
Some NETs, particularly carcinoid tumors, can lead to carcinoid syndrome. This syndrome is characterized by symptoms such as flushing, diarrhea, and wheezing and is caused by the release of excess hormones, such as serotonin, by the tumor.
It’s important to note that NETs are relatively rare, and patients may benefit from a multidisciplinary approach to their care, involving specialists in oncology, surgery, gastroenterology, and other relevant fields. Treatment decisions should be individualized based on the specific characteristics of the tumor and the patient’s overall health.