Cancer is one of the life threatening disease worldwide. There are over 100 different known cancers that affect humans. In 2012 about 14.1 million new cases of cancer occurred globally (except melanoma). It caused about 8.2 million or 14.6% of all human deaths. About 165, 000 children under 15 years of age were diagnosed with cancer in 2012. Although cancer comprises atleast 100 different diseases, all cancer cells share one important characteristic: they are abnormal cells in which the processes regulating normal cell division are disrupted. In other words, cancer develops from changes that cause normal cells to acquire abnormal functions. These changes are often the result of inherited mutations or induced by environmental factors such as UV light, X-rays, chemicals, tobacco products and viruses. All evidence suggests that most cancers are not the result of one single event or factor. Rather, around four to seven events are usually required for a normal cell to evolve through a series of premalignant stages into an invasive cancer. Often many years elapse between the initial event and the development of cancer. The development of molecular biological techniques may help in the diagnosis of potential cancers in the early stages even long before tumors are visible.