Three illustrations show abnormal and uncontrolled cell growth in cancer and each illustration is marked with the following text:

1. A cell begins to divide abnormally.
2. The cancer cells produce a tumor, which begins to displace normal cells and tissues.
3. Cancer cells are particularly dangerous because of their tendency to spread once they enter the bloodstream or lymph vessels. The cancer then moves into other parts of the body and forms secondary tumors, a process called metastasis.