Final answer:
Cancer results from the uncontrolled progression of the cell cycle, often due to DNA damage leading to rapid and abnormal cell division, forming tumors that can harm tissues and organs.
Step-by-step explanation:
Cancer occurs when the cell cycle proceeds without control, due to the breakdown of mechanisms that are supposed to regulate cell division. This unregulated division is typically due to a change in DNA sequence of genes responsible for controlling the cell cycle. These changes can result from environmental factors such as exposure to radiation or toxic chemicals, or from genetic predispositions. Consequently, the affected cells divide much faster than normal cells and may form a mass of abnormal cells known as a tumor, which can ultimately damage tissues and organs, and cause death.