Causes of Cancer
In majority of people cancer occurs for no particular cause, respectively the cause remains unknown. However, experts assume that transformation from normal into a cancer cells takes place gradually, progressing from a pre-cancerous lesion to malignant tumor. Such transformation is believed to be a result of interaction between one's genetic factors and external factors which can be divided in three categories :
1. physical carcinogens such as exposure to ultraviolet and ionizing radiation
2. chemical carcinogens such as tobacco smoke, asbestos and benzene
3. and biological carcinogens such as viral and bacterial infections (Human Papilloma Virus, Hepatitis B, HIV)
Factor which greatly increases the risk of cancer is also aging because cancer most frequently affects people older than 50 years. However, cancer can also occur in younger people and even children, while both men and women are in equal risk. Malnutrition and consumption of foods high in fats and low in fiber (fruits and vegetables), and excessive alcohol consumption is also proven to increase the risk of some types of cancer such as colorectal cancer.
About 20% of all cases of cancer is caused by genetic factors - inherited genetic mutation. The inherited genetic mutation is transfered from parents to children and thus the risk of cancer is greater in families which have a history of cancer. However, inherited genetic mutation does not necessarily mean that one will get cancer. If the risk is high the doctors usually recommend regular testing with purpose that if cancer does occur it can be detected and treated early. Risk of hereditary cancer have people whose relatives have cancer and/or family member or relative has more than one type of cancer.