what is cancer?

Cancer is a disease in which division of cells occurs in an unregulated manner. C ancer cells divide continuously to give rise to mass of cells (tumors). In early stages cancer does not show any noticeable effect. But the effect becomes severe with the increasing stage of cancer. The effect of formation of tumor depends upon the organ in which it is located. For example tumor in stomach causes bleeding from mouth. Localized pain and swelling may occur. Some general effects of cancer are sudden loss of weight, fever, excessive tiredness, patches on skin etc.