Cancer cells are essentially a new parasitic life form living inside of you. It is born from you but it is not you. It decided to play by its own rules and pursue its own goals, ignoring the signals that makes the host body functional. Often, it is attacked by the host body immune system like other intruders and it has to defend itself. Some cancer cell lines HeLa have well outlived their host and are used in scientific research.

In a way, cancer is life and life is cancer.