C ancer is a collection of diseases that have in common uncontrolled cell growth and the ability to invade the body.
Distant spread is called metastasis .
The ability to spread makes cancer a malignant disease. Malignant means that the disease, if not treated, can progress and lead to death. To begin to understand the complexities of why cancer appears, it is necessary to know something about cell growth. Tissues are composed of cells. Normal cells respond to specific chemical messages from other cells that either stimulate or inhibit their growth.