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Pancreatic cancer arises when cells in the pancreas, a glandular organ behind the stomach, begin to multiply out of control and form a mass. These cancer cells have the ability to invade other parts of the body. There are a number of types of pancreatic cancer. The most common, pancreatic adenocarcinoma, accounts for about 85% of cases, and the term "pancreatic cancer" is sometimes used to refer only to that type. These adenocarcinomas start within the part of the pancreas which make digestive enzymes. Several other types of cancer, which collectively represent the majority of the non-adenocarcinomas, can also arise from these cells. One to two in every hundred cases of pancreatic cancer are neuroendocrine tumors, which arise from the hormone-producing cells of the pancreas. These are generally less aggressive than pancreatic adenocarcinoma. Signs and symptoms of the most common form of pancreatic cancer may include yellow skin, abdominal or back pain, unexplained weight loss, light-colored stools, dark urine and loss of appetite. There are usually no symptoms in the disease's early stages, and symptoms that are specific enough to suspect pancreatic cancer typically do not develop until the disease has reached an advanced stage. By the time of diagnosis, pancreatic cancer has often spread to other parts of the body.〔 Pancreatic cancer rarely occurs before the age of 40, and more than half of cases of pancreatic adenocarcinoma occur in those over 70.〔 Risk factors for pancreatic cancer include tobacco smoking, obesity, diabetes, and certain rare genetic conditions.〔 About 25% of cases are linked to smoking, and 5–10% are linked to inherited genes.〔 Pancreatic cancer is usually diagnosed by a combination of medical imaging techniques such as ultrasound or computed tomography, blood tests, and examination of tissue samples (biopsy).〔〔 The disease is divided into stages, from early (stage I) to late (stage IV).〔 Screening the general population has not been found to be effective. The risk of developing pancreatic cancer is lower among non-smokers, and people who maintain a healthy weight and limit their consumption of red or processed meat. A smoker's chance of developing the disease decreases if they stop smoking, and almost returns to that of the rest of the population after 20 years.〔 Pancreatic cancer can be treated with surgery, radiotherapy, chemotherapy, palliative care, or a combination of these. Treatment options are partly based on the cancer stage. Surgery is the only treatment that can cure the disease; it may also be done to try to improve quality of life without the potential for cure. Pain management and medications to improve digestion are sometimes needed.〔 Early palliative care is recommended even for those receiving treatment that aims for a cure. In 2012, pancreatic cancers of all types were the seventh most common cause of cancer deaths, resulting in 330,000 deaths globally. Pancreatic cancer is the fifth most common cause of death from cancer in the United Kingdom,〔(Pancreatic Cancer Research Fund, 2015 )〕 and the fourth most common in the United States.〔. The top three vary by gender, and include breast cancer for women and prostate cancer for men.〕 The disease occurs most often in the developed world, where about 70% of the new cases in 2012 originated.〔 Pancreatic adenocarcinoma typically has a very poor prognosis: after diagnosis, 25% of people survive one year and 5% live for five years.〔〔 See p. 4 for incidence estimates, and p. 19 for survival percentages.〕 For cancers diagnosed early, the five-year survival rate rises to about 20%.〔 "The highest cure rate occurs if the tumor is truly localized to the pancreas; however, this stage of disease accounts for less than 20% of cases. In cases with localized disease and small cancers (<2 cm) with no lymph node metastases and no extension beyond the capsule of the pancreas, complete surgical resection is associated with an actuarial five-year survival rate of 18% to 24%."〕 Neuroendocrine cancers have better outcomes; at five years from diagnosis, 65% of those diagnosed are living, though survival varies considerably depending on the type of tumor.〔 ==Types== The many types of pancreatic cancer can be divided into two general groups. The vast majority of cases (about 99%) occur in the part of the pancreas which produces digestive enzymes, known as the exocrine component. There are several sub-types of exocrine pancreatic cancers, but their diagnosis and treatment have much in common. The small minority of cancers that arise in the hormone-producing (endocrine) tissue of the pancreas have different clinical characteristics. Both groups occur mainly (but not exclusively) in people over 40, and are slightly more common in men, but some rare sub-types mainly occur in women or children.〔 ((Table 5 ) outlines the proposed TNM staging system for PanNETs.)〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pancreatic cancer」の詳細全文を読む スポンサード リンク
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