What is Cancer?

Cancer is a group of more than 100 different diseases. Cancer occurs when cells become abnormal and keep dividing and keep forming more cells without control or order. All body organs are made up of cells which divide to produce more cells when needed. If these cells divide when new cells are not needed, they form a mass of excess tissue, called tumor. Tumors can be benign (not cancer) or malignant (cancer). These cells can invade and damage nearby tissue and organs. When this tumor spreads through blood stream or lymphatic system to form new tumor in other part of the body, it is called metastasis.