Diagnosis
Most cancers are initially recognized either because of the appearance of signs or symptoms or through screening. Neither of these lead to a definitive diagnosis, which requires the examination of a tissue sample by a pathologist. People with suspected cancer are investigated with medical tests. These commonly includeblood tests, X-rays, CT scans and endoscopy.
Most people are distressed to learn that they have cancer. They may become extremely anxious and depressed. The risk of suicide in people with cancer is approximately double the normal risk.[84]
Classification
Further information: List of cancer types and List of oncology-related terms
Cancers are classified by the type of cell that the tumor cells resemble and is therefore presumed to be the origin of the tumor. These types include:
- Carcinoma: Cancers derived from epithelial cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the breast, prostate, lung, pancreas, and colon.
- Sarcoma: Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve), each of which develops from cells originating in mesenchymal cells outside the bone marrow.
- Lymphoma and leukemia: These two classes of cancer arise from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. Leukemia is the most common type of cancer in children accounting for about 30%.[85]
- Germ cell tumor: Cancers derived from pluripotent cells, most often presenting in the testicle or the ovary (seminomaand dysgerminoma, respectively).
- Blastoma: Cancers derived from immature "precursor" cells or embryonic tissue. Blastomas are more common in children than in older adults.
Cancers are usually named using -carcinoma, -sarcoma or -blastoma as a suffix, with the Latin or Greek word for the organor tissue of origin as the root. For example, cancers of the liver parenchyma arising from malignant epithelial cells is calledhepatocarcinoma, while a malignancy arising from primitive liver precursor cells is called a hepatoblastoma, and a cancer arising from fat cells is called a liposarcoma. For some common cancers, the English organ name is used. For example, the most common type of breast cancer is called ductal carcinoma of the breast. Here, the adjective ductal refers to the appearance of the cancer under the microscope, which suggests that it has originated in the milk ducts.
Benign tumors (which are not cancers) are named using -oma as a suffix with the organ name as the root. For example, a benign tumor of smooth muscle cells is called a leiomyoma (the common name of this frequently occurring benign tumor in the uterus is fibroid). Confusingly, some types of cancer use the -noma suffix, examples including melanoma andseminoma.
Some types of cancer are named for the size and shape of the cells under a microscope, such as giant cell carcinoma,spindle cell carcinoma, and small-cell carcinoma.
Pathology
The tissue diagnosis given by the pathologist indicates the type of cell that is proliferating, its histological grade, genetic abnormalities, and other features of the tumor. Together, this information is useful to evaluate the prognosis of the patient and to choose the best treatment. Cytogenetics and immunohistochemistry are other types of testing that the pathologist may perform on the tissue specimen. These tests may provide information about the molecular changes (such asmutations, fusion genes, and numerical chromosome changes) that have happened in the cancer cells, and may thus also indicate the future behavior of the cancer (prognosis) and best treatment.
Prevention
Main article: Cancer prevention
Cancer prevention is defined as active measures to decrease the risk of cancer.[86] The vast majority of cancer cases are due to environmental risk factors, and many, but not all, of these environmental factors are controllable lifestyle choices. Thus, cancer is considered a largely preventable disease.[87] Between 70% and 90% of common cancers are due to environmental factors and therefore possibly preventable.[88]
Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: tobacco, overweight / obesity, an insufficient diet, physical inactivity, alcohol, sexually transmitted infections, and air pollution.[89] Not all environmental causes are controllable, such as naturally occurring background radiation, and other cases of cancer are caused through hereditary genetic disorders, and thus it is not possible to prevent all cases of cancer.
Dietary
Main article: Diet and cancer
While many dietary recommendations have been proposed to reduce the risk of cancer, the evidence to support them is not definitive.[9][90] The primary dietary factors that increase risk are obesity and alcohol consumption; with a diet low in fruits and vegetables and high in red meat being implicated but not confirmed.[91][92] A 2014 meta-analysis did not find a relationship between fruits and vegetables and cancer.[93] Consumption of coffee is associated with a reduced risk of liver cancer.[94] Studies have linked excessive consumption of red or processed meat to an increased risk of breast cancer,colon cancer, and pancreatic cancer, a phenomenon that could be due to the presence of carcinogens in meats cooked at high temperatures.[95][96] This was confirmed in 2015 by the IARC of the World Health Organization, which determined that eating processed meat (e.g., bacon, ham, hot dogs, sausages) and, to a lesser degree, red meat was linked to some cancers.[97][98]
Dietary recommendations for cancer prevention typically include an emphasis on vegetables, fruit, whole grains, and fish, and an avoidance of processed and red meat (beef, pork, lamb), animal fats, and refined carbohydrates.[9][90]
Medication
The concept that medications can be used to prevent cancer is attractive, and evidence supports their use in a few defined circumstances.[99] In the general population, NSAIDs reduce the risk of colorectal cancer, however due to the cardiovascular and gastrointestinal side effects they cause overall harm when used for prevention.[100] Aspirin has been found to reduce the risk of death from cancer by about 7%.[101] COX-2 inhibitor may decrease the rate of polyp formation in people with familial adenomatous polyposis, however it is associated with the same adverse effects as NSAIDs.[102] Daily use of tamoxifen or raloxifene has been demonstrated to reduce the risk of developing breast cancer in high-risk women.[103] The benefit versus harm for 5-alpha-reductase inhibitor such as finasteride is not clear.[104]
Vitamins have not been found to be effective at preventing cancer,[105] although low blood levels of vitamin D are correlated with increased cancer risk.[106][107] Whether this relationship is causal and vitamin D supplementation is protective is not determined.[108] Beta-Carotene supplementation has been found to increase lung cancer rates in those who are high risk.[109] Folic acid supplementation has not been found effective in preventing colon cancer and may increase colon polyps.[110] It is unclear if selenium supplementation has an effect.[111]
Vaccination
Vaccines have been developed that prevent infection by some carcinogenic viruses.[112] Human papillomavirus vaccine(Gardasil and Cervarix) decreases the risk of developing cervical cancer.[112] The hepatitis B vaccine prevents infection with hepatitis B virus and thus decreases the risk of liver cancer.[112] The administration of human papillomavirus and hepatitis B vaccinations is recommended when resources allow.[11
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