The Pancreatic Neuroendocrine Tumor
A pancreatic neuroendocrine tumor is a type of neoplasm that develops in the islet cells of the pancreas. Called islets of Langerhans, these cells are endocrine cells. They produce hormones and compose about 1 to 2 percent of the pancreas's cell mass. A healthy adult pancreas contains about a million islets that dot the structure. Together they weigh about 1 to 1.5 grams. In an islet around one thousand cells reside.
Pancreatic neuroendocrine tumors, also called islet-cell tumors, are very rare and commonly slow growing. About sixty percent of the tumors, excluding insulinomas, are malignant. Tumors that occur in the exocrine cells of the pancreas are far more common. Islet-cell tumors have an incidence rate of about five cases for every one million people each year. Research shows that only two or three thousand cases are diagnosed per year in the United States. However, some studies seem to show that, based on the evidence of autopsies, pancreatic neuroendocrine tumors may be more common than expected.
Neuroendocrine tumors usually occur in the triangle composed of the common and cystic hepatic ducts, the bottom border of the pancreas, and the second and third sections of the duodenum (the upper part of the small intestine). There are two types of pancreatic neuroendocrine tumors: functional, or productive, tumors and nonfunctional tumors. Functional tumors secrete hormones whereas nonfunctional tumors do not. Productive tumors are usually found because of the symptoms their hormones cause. For instance, insulinomas, which produce insulin, cause hypoglycemia due to the hormone's blood-sugar lowering ability. This symptom can be alleviated by food intake.
Other common and more generalized symptoms include tremors, nausea, episodic sweating, weight gain, rapid heart rate, hunger, and even central nervous system problems such as seizures. Insulinomas usually occur most often in women between 40 and 50 years of age. The tumors are typically small and solitary. They usually grow on the pancreas itself. Only ten percent of them are cancerous. Another type of functional pancreatic neuroendocrine tumors is the gastrinoma. These tumors secrete the hormone gastrin in large amounts. Gastrin has the responsibility of prodding the stomach to secrete gastric acid. G cells in the stomach and duodenum normally create the hormone. In the stomach, gastrin's presence triggers parietal cells to secrete hydrochloric acid (HCL). This strong acid breaks down food in the stomach. When gastrin is over-secreted, a condition called Zollinger-Ellison syndrome occurs. Three symptoms compose the disorder: gastric hyperacidity and hyper-secretion (related to heartburn), the related pancreatic neuroendocrine tumor, and peptic ulcer occurrence. In fact, around two percent of people with peptic ulcers that do not heal are later diagnosed with Zollinger-Ellison syndrome. Over half of all cases occur in males age 60 or older. A third kind of pancreatic neuroendocrine tumor is a glucagonoma. This secretes insulin's antagonist, glucacon. The tumors cause mild diabetes and often serious dermatitis. This kind of growth is usually large (two inches or more in diameter) when it is finally diagnosed. Seventy percent of glucagonomas are cancerous. Though insulinomas, gastrinomas, and glucagonomas are the most common, other pancreatic neuroendocrine tumors are vasoactive inesteinal polypeptides, somatostatinomas, and pancreatic polypeptides. Many types of pancreatic neuroendocrine tumors exist. Thus it is important to be aware of them and their symptoms. A quick diagnosis and treatment can mean the difference between a minor, easily fixed problem, and a life-threatening disease.
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