..okay, I found the definition of IV-A
I'll post it, just in case anyone else needs to know:
Stage IV is divided into stages IVA, IVB, and IVC. In stage IVA, the tumor has spread to nearby tissues in the lip and oral cavity (mouth); and/or cancer has spread to one or more lymph nodes in the neck and the involved lymph nodes are 6 centimeters (about 2 inches) or smaller.