07-12-2017, 09:15 AM
Cancer is a group of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread to other parts of the body. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. While these symptoms may indicate cancer, they may have other causes. More than 100 types of cancer affect humans.
Tobacco use is the cause of around 22% of deaths from cancer. Another 10% is due to obesity, poor diet, lack of physical activity and excessive consumption of alcohol. Other factors include certain infections, exposure to ionizing radiation and environmental pollutants. In the developing world, almost 20% of cancers are due to infections such as hepatitis B, hepatitis C, and human papillomavirus infection. These factors act, at least in part, by changing the genes of a cell. Normally, many genetic changes are required before the cancer develops. Approximately 5-10% of cancers are due to genetic defects inherited from a person's parents. Cancer can be detected by certain signs and symptoms or screening tests. Then, typically, it is further investigated by medical images and confirmed by a biopsy.