Table 1.

T classification of oral cancer, 8th edition [74]

Tumor category	Tumor characterization
TX	Primary tumor cannot be examined
Tis	Carcinoma in situ
T1	Tumor ≤ 2 cm, ≤ 5 mm DOI
T2	Tumor ≤ 2 cm, DOI ≤ 5 mm and ≤ 10 mm or tumor > 2 cm but ≤ 4 cm and ≤ 10 mm DOI
T3	Tumor > 4 cm or any tumor > 10 mm DOI
T4	Moderately advanced or very advanced local disease
T4a	Tumor involves adjacent structures, such as the cortical bone, deep extrinsic muscles of the tongue, maxillary sinus, or skin of the face.
T4b	Tumor involves masticator space, pterygoid plates, or skull base and/or encases the internal carotid artery.