As I do further research on this thing, it just seems like the thing we need to be most worried about is not the size of the tumor, not so much on whether or not it has spread into adjacent structures, but whether or not any lymph nodes are involved.
Here’s how these things are staged.
A tumor 2cm or smaller is a T1. Bigger than 2cm but smaller than 4cm, T2. Bigger than 4cm, T3. Tumor that invades nearby structures, like base of tongue, mandible, hard palate, etc., T4.