Table 2.

TNM classification of carcinomas of the lip and oral cavity (54).

Stage	Explanation
Primary Tumor
T0	No evidence of primary tumor
TIS	Carcinoma in situ
T1	Tumor size 2cm or smaller, 5mm deep or less
T2	Tumor ≤ 2cm, >5mm and ≥ 10mm depth of invasion or tumor> 2cm but ≤ 4cm and depth of invasion ≤ 10mm
T3	Larger than 4cm, or deeper than 10mm
T4a	Extrinsic muscle of the tongue removed, included extensive tumors with bilateral tongue involvement and/or DOI>20 mm.
T4b	Very advanced locally disease definition; tumor invades masticator space, pterygoid plates, skull base, and/or encases the internal carotid artery.
Regional lymph nodes (N)
N0	The lymph nodes don’t contain cancer cells.
N1	Metastases to the single lymph node. The node is no larger than 3cm across. Node must be extranodal extension negative.
N2a	Metastases to multiple ipsilateral nodes, and the node is between 3cm and 6cm across. Nodes must be extranodal extension negative or single ipsilateral or node 3cm or smaller with extranodal extension.
N2b	Metastases to multiple ipsilateral nodes, and the node is between 3cm and 6cm across. The Nodes must be extranodal extension negative.
N2c	metastases to bilateral nodes or contralateral nodes none >6 cm. Nodes must be extranodal extension negative
N3	Metastases to nodes >6 cm
N3a	Metastases to nodes >6 cm but extranodal extension negative.
	single ipsilateral nodes in machine learning >3 cm in greatest dimension with extranodal extension or multiple ipsilateral, contralateral, or bilateral nodes, any with extranodal extension or single contralateral node 3cm or smaller and with extranodal extension.