cancer

Definition: Mutation of DNA in a single cell to divide without control. If unchecked Cancer cells can invade nearby tissues and spread through the bloodstream and lymphatic system to other parts of the body (metastasis) .
Cancer cells are smart in avoiding natural cell death and settle in most conducive locations like bones & other organs where nourishment supply is abundant.
A tumor is an abnormal mass of tissue developed from excessive cell division (mitotic activity)which has no useful body function. It may be either benign or malignant.
Real battle is on in the metastasis stage between the Immune system and the Tumor.