Floor of the mouth cancer forms when a genetic mutation turns normal, healthy cells into abnormal cells. Healthy cells grow and multiply at a set rate, eventually dying at a set time. Abnormal cells grow and multiply out of control, and they don’t die. The accumulating abnormal cells form a mass (tumor).
https://www.mayoclinic.org/diseases-conditions/floor-mouth-cancer/symptoms-causes/syc-20354179

