Table 4.

Summary of the AJCC 6th edition, AJCC 7th edition, UICC, and BWH tumor- (T-) stage systems.

T-stage	AJCC 6th	AJCC 7th	UICC	T-stage	BWH
T1	Tumor 2 cm or less in greatest dimension	Tumor <2 cm in greatest dimension with fewer than two “high-risk” features∗	Tumor ≤2 cm in largest horizontal size	T1	0 high-risk factors‡
T2	Tumor more than 2 cm but not more than 5 cm in greatest dimension	Tumor >2 cm in greatest dimension or tumor any size with two or more “high-risk” features∗	Tumor >2 cm in largest horizontal size	T2a	1 high-risk factor‡
				T2b	2-3 high risk factors‡
T3	Tumor more than 5 cm in greatest dimension	Tumor with invasion of orbit, maxilla, mandible, or temporal bones	Deep infiltration (skeleton muscle, cartilage, or bone)	T3	≥4 high risk factors‡
T4	Tumor invades deep extradermal structures (i.e., cartilage, skeleton muscle, or bone)	Tumor with invasion of skeleton (axial or appendicular) or perineural invasion of skull base	Infiltration of base of skull or vertebra	T4	n/a

*AJCC high-risk factors include >2 mm thickness, Clark level ≥IV, perineural invasion, primary site ear, primary site non-hair-bearing lip, or poorly differentiated histology.

^‡BWH “high-risk” factors include tumor diameter ≥2 cm, poorly differentiated histology, perineural invasion ≥0.1 mm, or tumor invasion beyond fat (excluding bone invasion which automatically upgrades tumor to BWH stage T3).