Cancer (medical term: malignant neoplasm) is a class of diseases are a group of cells display''''Uncontrolled growth (division beyond the normal limits), invasion''''( intrusion and damage to Surrounding tissue), and Sometimes' '''metastasis (spread to other locations within the body via lymph or blood).
These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, and do not invade or metastasize.
Most cancers form a tumor but some, like leukemia, do not.Branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer oncology.Cancer can affect people of all ages, even fetuses, but risk for most varieties increases with age. Cancer causes about 13% of all human deaths. According to the American Cancer Society, 7.6 million people died of cancer in the world during 2007. Cancer can affect all animals.
Nearly all cancers are caused by abnormalities in the genetic material of the transformed cells. These abnormalities may be due to the effects of carcinogens, such as cigarette smoke, radiation, chemicals, or infectious agents. Other cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or inherited, and thus present in all cells from birth.
Heritability of cancers are usually affected by complex interactions between carcinogens and the host genome. New aspects of the genetics of cancer pathogenesis, such as DNA methylation, and microRNAs are increasingly recognized as important.
Genetic abnormalities found in cancer typically affect two general classes of genes. Cancer-promoting oncogenes are typically activated in cancer cells, giving cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments. Suppressor gene''tumor''yang then inactivated in cancer cells, resulting in loss of normal function in cells, such as accurate DNA replication, control over the orientation of the cell cycle, and adhesion within tissues, and interaction with protective cells of the immune system.
Diagnosis usually requires histological examination of tissue biopsy specimen by a pathologist, although the initial indication of malignancy can be symptoms or radiographic imaging abnormalities. Most cancers can be treated and some cured, depending on the specific type, location, and stage.
Once diagnosed, cancer is usually treated with a combination of surgery, chemotherapy and radiotherapy. As work progressed, the treatment becomes more specific for different varieties of cancer.
There was significant progress in the development of targeted therapy drugs that work specifically on detectable molecular abnormalities in certain tumors, and which minimize damage to normal cells.
Prognosis of cancer patients who are most influenced by the type of cancer, as well as the stage, or extent of disease. In addition, histological assessment and the presence of specific molecular markers can also be useful in establishing prognosis, as well as in determining individual treatments.
