Tumors Of the Pancreas (Pancreatic Neuroendocrine Tumors)

Pancreas is a glandular organ attached to the duodenum, which is the first portion of the small intestine. Pancreas has both exocrine and endocrine functions. While the exocrine gland cells produce the pancreatic juice which aids the digestion of food, the endocrine cells produce hormones. The tumors arising from the endocrine gland cells may be benign or malignant. Some may be functioning tumors secreting hormones; others may be nonfunctioning. Functioning tumors often result in syndromes caused by the overproduction of hormones. It is not just the malignant and functional tumors that cause problems; non functional benign tumors also can cause blockage in the small intestine or obstruction to the drainage of bile. They can cause bleeding too.

INSULINOMA

A pancreatic endocrine tumor that secretes the hormone insulin is called insulinoma. Lowering of the blood sugar level is the effect produced by the hormone insulin. Insulinomas are rare tumors and 90% of them are noncancerous.

Symptoms

The typical symptoms of insulinoma are the same symptoms produced by hypoglycemia or abnormally low blood sugar level. When a person has fasted for several hours, especially in the morning after a long night without food, weakness, sweating, palpitations and trembling may be felt. Extreme hunger, headache, vision problems, confusion and personality changes are also other symptoms. Hypoglycemia can cause seizures, fainting or even coma, if measures to elevate the blood sugar is not undertaken.

Diagnosis and Treatment

Diagnosing an insulinoma can be difficult by regular blood tests. High levels of insulin in the blood, with low levels of blood glucose, are indicative of insulinomas, but to determine the condition, the blood tests have to be conducted exactly when the patient displays the symptoms. Often, the patients are admitted in the hospital to artificially create conditions such as prolonged starvation, which produce the symptoms. The patient stays without food for 24 to 72 hours until symptoms appear, and then the blood glucose levels are measured. This test will help in ascertaining the presence of functioning insolinomas.

 Once the presence of insulinoma is established through blood tests, the location of the tumor has to be identified.  Ultra sonography tests with the ultra sound probe inserted into the intestine with the help of endoscope gives better images of the pancreatic tumors. Pet scans are also used for better imaging of the tumors, but occasionally, surgery may be required to find the tumor. If the tumor is found during exploratory surgery, it is removed immediately. If the tumor is completely removed, it cures the disease, but symptoms may continue with incomplete removal. Drugs such as diazoxide and Octreotide help in preventing acute hyperglycemia which may result from excess insulin production by the remaining tumor cells. Chemotherapy drugs streptozotocin and 5-fluorouracil are found to retard the growth of these tumors.

 GASTRINOMA

An abnormal growth in the pancreas or the first part of the small intestine called duodenum may be a gastrinoma if it is secreting the hormone gastrin. The function of the hormone gastrin is to trigger the production of digestive enzymes and acids by the stomach. Overproduction of gastrin will result in the overproduction of digestive acids which in turn cause peptic ulcers.

gastrinomas usually occur in clusters, and in half the cases, they are malignant. They occur either inside the pancreas or very near it. A hereditary condition called multiple endocrine neoplasia predisposes people to the development of tumors from glandular tissue in various organs producing hormones. The pancreas which has special cells producing the hormone insulin is one such glandular organ usually affected by this inherited disorder.

Symptoms and Diagnosis

Zollinger-Ellison syndrome characterized by the occurrence of a severe form of peptic ulcer in the stomach and the small intestine is usually caused by the gastrinomas in the pancreas. Though a quarter of the Zollinger-Ellison syndrome cases may not have gastrinomas, doctors are alerted to the possibility of this tumor when they come across aggressive forms of peptic ulcers and when the ulcers do not respond to the usual treatments. Zollinger-Ellison syndrome is a potentially fatal condition which can cause intestinal bleeding, and rupture of the intestine. All the people with gastrinomas do not have Zollinger-Ellison syndrome; mild peptic ulcer and diarrhea may be the symptoms in half the cases.

Frequent incidence of peptic ulcer alerts a doctor to the possibility of gastrinoma. When the usual treatment for peptic ulcer is found to be ineffective also, gastrinoma is investigated. A test to detect the blood levels of gastrin is done. Abnormally high levels of gastrin will conclusively prove the presence of gastrinoma.

After gastrinoma is detected, imaging tests are conducted to detect its exact location. Ultrasound testing with the aid of endoscope, CT scan, and PET scan, are some of the tests available. An x-ray, taken after the injection of a radio opaque dye into the artery supplying the pancreas, also is a useful test to find the tumor. Gastrinomas are usually very small and hard to locate.

Treatment

Temporary relief from the distressing symptoms may be obtained by the use of proton pump inhibitors; but large doses may be needed. Removing the gastrinoma by surgery may cure the disease in 20% of cases. If the above treatments are not effective, total gastrectomy may be the only option, in which the entire stomach is surgically removed. The gastrin produced by the gastrinoma cannot influence the stomach glands to produce the peptic ulcer-causing stomach acids any more. Lifelong oral supplementation of calcium and iron, and B12 injections, are essential because those minerals and vitamins can no longer be obtained from food, when the digestive juices produced by the stomach are absent.

When the cancer has spread to tissues and organs elsewhere in the body, the patient is treated with chemotherapy, which may not cure the cancer, but may help in reducing the symptoms. It can retard the growth and spread of the tumor and reduce the gastrin production. Gastrinomas usually have a fatal outcome.

VIPOMA

A rare tumor of the pancreas producing a substance called vasoactive intestinal peptide, or VIP for short, is termed vipoma. The action of this peptide results in severe, chronic, diarrhea with thin, watery stools.

More than half to three quarters of the vipomas are malignant. People who have the inherited condition called multiple endocrine neoplasia have a higher chance of developing vipoma.

Symptoms

Severe diarrhea, producing one to three quarts (1liter to 3 liters) of stools, is the main symptom of vipoma. The watery diarrhea causes dehydration and fatigue. The severity of the symptom may vary from time to time, or constant diarrhea may be present.

Conditions such as hypokalemia and acidosis may develop, because the constant diarrhea results in the loss of potassium salts and makes the blood acidic. Abdominal cramps, nausea and vomiting, muscular weakness and lethargy are caused by the deficiency of minerals and vitamins.

Diagnosis and Treatment

The initial diagnosis is based on the symptoms described by the patient. If a blood test shows abnormally high levels of vasoactive intestinal peptide, it is conclusive proof of vipoma. When the disease is identified, imaging tests to locate the tumor are conducted. PET scan and endoscopic ultrasound scan may be able to locate the vipoma before surgery is done.

Rehydrating the patient and replenishing the body with all the minerals and salts lost through the constant watery diarrhea is the first challenge in treating the symptoms of vipoma. Oral rehydration preparations, as well as bicarbonates to prevent acidosis, are given. But since the diarrhea is almost constant, keeping up the rehydration regimen is also a constant battle.

Removing the tumor surgically is the best option. In the early stages, before the tumors have spread, surgery effectively cures the disease in half the cases of vipoma. Even after the tumors have spread, surgery may be done to get relief from the distressing symptoms. Chemotherapy offers no benefit in either curing the condition or in relieving the symptoms. Octreotide is an effective drug for reducing diarrhea, but only when it is administered in high doses.

GLUCAGONOMA

A functioning pancreatic tumor producing the hormone glucagon is termed glucagonoma. The overproduction of glucagon has the effect of elevating the blood sugar levels. A characteristic rash is also another symptom.

Glucagonomas are malignant in 80% of the cases, but since they are slow growing tumors, most people with the disease live for more than 15 years from the onset of symptoms. 80% of the cases are found in women. The symptoms of glucagonomas usually start appearing around the age of fifty.

Symptoms and Diagnosis

The overproduction of glucagon by the tumor causes the characteristic symptoms of Type II diabetes. Weight loss may be one of the first symptoms noticed. Another characteristic symptom found in 90% cases is a skin rash which is brownish red in color and causes scaling. It may start in the groin area and may affect forearms, legs and buttocks too. This condition is called necrolytic migratory erythema and it is often accompanied by other symptoms such as cracking at the corners of the mouth and a bright red tongue which may look smooth and shiny.

A blood test which detects abnormally high levels of the hormone glucagon in the blood is the conclusive evidence of the presence of glucagonoma. Once the tumor is confirmed, its location is determined by imaging tests such as CT scan and endoscopic ultrasound scan. If the tumor is not detected by CT scan, a PET scan or an MRI may be necessary.

Treatment

Surgical removal of the growth is the ideal treatment to get complete relief from symptoms. If the tumor is too widespread for effective surgical removal, chemotherapy may help reduce the symptoms produced by the overproduction of the hormone glucagon. Chemotherapy is neither a cure for the condition nor does it help in prolonging life. It is a temporary measure to alleviate the symptoms and ensure a better quality of life.

Blood levels of glucagon may be brought down by the drug octreotide which increases appetite, thereby helping in gaining weight. The rash also may disappear with this medication. But elevation of blood glucose levels is a side effect. Intravenous administration of fatty acids and amino acids and topical application of Zinc ointments are other treatments which may relieve the rash.

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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