80% are considered idiopathik- meaning the cause is unknown. There are several risk factors that increase the chance of cancer:
Age: The most important risk factor for cancer is growing older. Most cancers occur in people over the age of 65. However, people of all ages, including children, can get cancer, too.
Inherited conditions: Some families are more susceptible to get certain cancers. Remember you cannot inherit cancer it’s just that you may be more susceptible to get it.
A. Lifestyle habits
Smoking: tar from cigarettes can lead to the cancer of lung, larynx (voice box), mouth, esophagus, bladder, kidney, throat, stomach, pancreas, or cervix. They also are more likely to develop acute myeloid leukemia (cancer that starts in blood cells).
Diet: high fat, high cholesterol diets increase risk. Studies suggest that people whose diet is high in fat have an increased risk of cancers of the colon, uterus, and prostate.
Obesity: Lack of physical activity and being overweight are risk factors for cancers of the breast, colon, esophagus, kidney, and uterus.
Alcohol: Having more than two drinks each day for many years may increase the chance of developing cancers of the mouth, throat, esophagus, larynx, liver, and breast. The risk increases with the amount of alcohol that a person drinks. For most of these cancers, the risk is higher for a drinker who uses tobacco.
Hepatitis B and hepatitis C viruses: Liver cancer can develop after many years of infection with hepatitis B or hepatitis C.
Human immunodeficiency virus (HIV): HIV is the virus that causes AIDS. People who have HIV infection are at greater risk of cancer, such as lymphoma and a rare cancer called Kaposi's sarcoma.
Helicobacter pylori: This bacterium can cause stomach ulcers. It also can cause stomach cancer.
C. Chemicals: Formalin, carbide.
People exposed to radiation like X Rays, UV light may have an increased risk of cancer, especially leukemia and cancers of the thyroid, breast, lung, and stomach. Ionizing radiation can cause cell damage that leads to cancer.