Final answer:
Cancer is a group of diseases characterized by abnormal cell growth and uncontrolled cell division and growth. The key feature that classifies a disease as cancer is the loss of regulation of the cell cycle due to DNA damage. This leads to the formation of tumors that can invade other tissues and organs.
Step-by-step explanation:
Cancer is a group of diseases characterized by abnormal cell growth that has the potential to invade or spread to other parts of the body. The key feature that classifies a disease as cancer is uncontrolled cell division and growth. This occurs when the cell cycle, which regulates cell division, is no longer regulated due to DNA damage. Cancer cells divide more quickly than normal cells and may form tumors that can invade other tissues and organs.