Floor of the mouth (under the tongue) … The accumulating abnormal mouth cancer cells can form a tumor. With time they may spread inside the mouth and on to other areas of the head and neck or other parts of the body. Mouth cancers most commonly begin in the flat, thin cells (squamous cells) that line your lips and the inside of your mouth. …
https://www.mayoclinic.org/diseases-conditions/mouth-cancer/symptoms-causes/syc-20350997

