T category T criteria
T3 Limited to the mucosa and immediately underlying soft tissue irrespective of thickness or greatest dimension
T4 Moderately or highly advanced
T4a Involving deep soft tissue ,cartilage ,bone ,or overlying skin
T4b Involving brain, dura ,skull base ,lower cranial nerves (IX, X , XI, XII ),masticator space ,carotid artery ,prevertebral space , or mediastinal structure