Why do cancer cells differ from normal cells?

Cancer cells differ from normal cells primarily because they do not stop growing and dividing. Unlike normal cells, which have regulated growth cycles and mechanisms to halt division when necessary, cancer cells often have mutations that disrupt these regulatory pathways. This uncontrolled proliferation is a hallmark of cancer, allowing these cells to multiply rapidly. As a result, they can form tumors, invade surrounding tissues, and lead to the development of metastatic cancer, further contributing to their malignancy.

The other options illustrate characteristics or behaviors that are not as defining or specific to cancer cells. While benign tumors may arise from precancerous cells, they do not characterize malignant cancer cells. Regarding spreading between individuals, cancer typically does not spread from person to person like infectious diseases. Finally, apoptosis, or programmed cell death, is a process that cancer cells often evade rather than undergo, allowing them to survive longer than normal cells.