Sunday, July 24, 2011

Classification of Pancreatic Tumors

Benign and Malignant Pancreatic Tumors

Before getting to the point of reviewing different types of pancreatic cancers, we would like to point out that not all the pancreatic tumors are in fact cancerous.

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Benign Pancreatic Tumors

The term "benign" refers to any substance that isn’t harmful or life-threatening. When referring to tumors, benign describes tumors that are non-cancerous. Most cases of benign pancreatic tumors occur as cystic tumors, growths that develop within a cyst’s membrane.

However, while cystic tumors such as mucinous cystadenoma and serous cystadenoma are typically harmless, the cystic tumor known as mucinous ductal ectasia is marked by a linking of potentially malignant cells that can eventually lead to the development of pancreatic cancer.

Symptoms of benign pancreatic tumors are nearly identical to those of the malignant type:
  • abdominal pain
  • back pain
  • digestive problems
  • nausea.

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As a result, doctors use the same diagnostic procedures to evaluate whether or not a growth is a benign pancreatic tumor.

Malignant Pancreatic Tumors

Cancerous pancreatic tumors are referred to as malignant. Unfortunately, once a person starts to feel the symptoms of malignant pancreatic tumors, the pancreatic cancer has generally advanced to later stages, in which it is highly likely that cancer has spread (metastasized) to other parts of the body.

Because malignant pancreatic tumors are usually diagnosed after the cancer has progressed into later stages, the prognosis for malignant pancreatic tumors is disheartening: Less than 20 percent of pancreatic cancer patients survive more than a year after their diagnosis.

As a result, living a healthy lifestyle, understanding your genetic predisposition and the disease symptoms, and getting regular physical exams are the best approaches to prevent the development of malignant pancreatic tumors.

Types of Pancreatic Cancer

There are many types of pancreatic cancer that can be developed in human body. Though they differ in their speed of growth and propensity to spread, all pancreatic cancers share some similarities. First, all start as abnormal growths or tumors. These growths appear when the DNA of cells is mutated by carcinogens like tobacco, pesticides, and pollutants. These mutated cells multiply rapidly. They form tumors, which then spread by direct growth and metastasis, which occurs when cells split from the tumor to colonize other areas of the body.

There are several ways of the pancreatic cancer classification. They can be grouped according to where in the pancreas the cancer is or according to the type of cell the cancer has originated from. In terms of the location, cancer may affect the head, body or tail of the pancreas. Between 70 and 80% of pancreatic cancers are in the head of the pancreas.

The pancreas has two main types of cells, exocrine and endocrine. Each type can form different malignancies or benign tumors.

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Exocrine Pancreatic Cancer

The vast majority of cancers of the pancreas are exocrine in type. This means that they start in the cells of the exocrine pancreas, which produces the digestive pancreatic juices. These are released into channels, or ducts, within the pancreas, and pass through the main pancreatic duct into the duodenum. There are a number of different types of exocrine pancreatic cancers.

More than 9 out of 10 exocrine pancreatic cancers are adenocarcinomas. Nearly all of these are ductal adenocarcinomas. These cancers start in the cells lining the ducts of the pancreas, occuring on the surface layer of the pancreas either on the head, body, or tail of the gland. Many occur on the head, which improves the prognosis because the tumors are usually discovered early due to the growths' symptoms. But if the tumors grow on the body or tail, symptoms only appear when the cancer has reached late stages. Adenocarcinomas are the most deadly type of pancreatic cancer. They are resistant to many treatments and grow rapidly. People diagnosed with this type usually only live 5 to 12 months. And the mortality rate of cases is about 95 to 97 percent.

There are rarer types of exocrine pancreatic cancer. The treatment for these rare types is more or less the same as for ductal adenocarcinoma. So surgery is the main treatment, if that is possible. The other rarer types of exocrine pancreatic cancer are
  • Cystic tumors. Cystic tumors cause a cyst or fluid filled sac in the pancreas. Most pancreatic cysts are benign, but some are cancerous. Cystic cancers can have a better outlook (prognosis) than other types of exocrine pancreatic cancer.
  • Cancer of the acinar cells. The acinar cells are at the ends of the ducts that produce the pancreatic juices.
  • Sarcomas of the pancreas. These are cancers of the connective tissue holding together the cells of the pancreas. They are very rare and most often occur in children.

Endocrine Pancreatic Cancer

Endocrine tumors are uncommon. They start in the endocrine pancreas, where insulin and other hormones are made and released directly into the bloodstream. They are also called neuroendocrine tumors or islet cell tumors. 

About a third of these tumors produce hormones, which can cause some strange symptoms. Most of these tumors are non cancerous (benign). They are named after the hormone they produce
  • Gastrinomas produce a hormone called gastrin,which stimulates the stomach to secrete acid and enzymes, causing peptic ulcers. Gastrinomas is a cluster of tumors in or near the pancreas. About half of these tumors are cancerous. Sometimes a gastrinoma occurs as part of multiple endocrine neoplasia, a hereditary problem which is caused by the endocrine glands. Diarrhea is the first symptom for this tumor. Frequent ulcers and abdominal pain can also be the symptoms. These tumors are very small and difficult to locate. If oral medicines are not enough then surgically the stomach is removed.
  • Insulinomas produce insulin. Insulinomas are very rare, and less than 10 percent cause cancer. One of the more malignant cancer types is the cystadenoma. But only around half of these growths become malignant. And when they are diagnosed as cancerous, they are more treatable than the other types.
  • Somatostatinomas produce a hormone called somatostatin. They are very rare, with only forty three or so cases reported. The tumor's presence produces diabetes mellitus, imbalances in hormones made by the pancreas, gallstones, and anemia.
  • VIPoma, or vasoactive intestinal peptide tumor, is a tumor that produces excessive amounts of the hormone it's named for. Vasoactive intestinal peptide helps control how water transport is handled and transported in the digestive tract. The main symptom is diarrhea.
  • Glucagonomas produce a hormone called glucagon. This tumor type causes high levels of glucagon that produces hyperglycemia, which is high blood sugar. The resulting symptoms are rashes (necrolytic erythema migrans), venous thrombosis, mental disturbances, and anemia result. Mild glucose intolerance is found in 90 percent of people with glucagonomas.
  • PPomas are named for the secretion of pancreatic polypeptide (PP) hormone. The hormone's role is not understood. Abdominal pain and diarrhea result.
  • GNRHomas encourage the secretion of human growth hormone. This controls growth, and an over secretion causes acromegaly.
  • ACTHoma create adrenocorticotropic hormone, and almost all are cancerous. The hormone stimulates the adrenal cortex to produce cortisol. Cortisol increases blood pressure and blood sugar, and suppresses the immune system.

Two thirds of pancreatic endocrine tumors are called non functioning tumors as they do not produce any hormones or symptoms. Most of these tumors are cancer (malignant). 

Endocrine pancreatic tumors are treated differently to exocrine tumors and generally have a much better outlook (prognosis) than adenocarcinoma of the pancreas. These tumors are not always cancerous, but most stand a good chance of becoming malignant. Of the types of pancreas neuroendocrine tumors, the chances for malignancy are fairly high: glucagonomas (50-80 percent are malignant), somatostatinomas (70%), VIPomas (40-70%), PPomas (>60%), GNRHomas (60%), gastrinomas (60-90%), ACTHomas (>95%), and insulinomas (<10%).

Lymphoma of the Pancreas

Lymphoma of the pancreas is a very rare disease. Lymphoma is a cancer of the lymphatic system of the body. As the lymphatic system runs throughout the body, it can crop up anywhere. Because it is a different type of cancer, it is treated differently to the other types of pancreatic cancer.

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