Tumor initiation is defined as "a process in which normal cells are changed so that they are able to form tumors".[1] It is the first phase in tumor development.[2]Mutagens, substances that cause cancer can be tumor initiators.
^Compton C (2020). "Cancer initiation, promotion, and progression and the acquisition of key behavioral traits.". Cancer: The Enemy from Within. Cham: Springer. pp. 25–48. doi:10.1007/978-3-030-40651-6_2. ISBN978-3-030-40650-9.