Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells.

Cancer arises when normal cells transforms into the tumor cells. It occurs in a multistage process that generally progresses from a pre-cancerous lesion to a malignant tumor. Cancer cell arises by the interaction between a person’s genetic factors withthree categories of external agents, including:

• physical carcinogens, such as ultraviolet and ionizing radiation;
• chemical carcinogens, such as asbestos, components of tobacco smoke, aflatoxin (a food contaminant), and arsenic (a drinking water contaminant); and
• biological carcinogens, such as infections from certain viruses, bacteria, or parasites.

Another fundamental factor for the development of cancer is ageing. The incidence of cancer rises with age because the mechanisms of cellular repair becomes less effective as a person grows older.

In cancer there is rapid creation of abnormal cells that rapidly grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs, this spreading of trusted online pharmacy reviews to other parts of the body is referred to as metastasizing. Metastases are a major cause of death from cancer.