Table 6.

T classification for cutaneous squamous cell carcinoma according to Brigham and Women’s Hospital staging system.

	T Category
TX	Primary tumor cannot be identified
T0	Carcinoma in situ
T1	Primary tumor without risk factors
T2a	Primary tumor with 1 risk factor
T2b	Primary tumor with 2–3 risk factors
T3	Primary tumor with 4 risk factors or bone invasion
Risk factors	• Tumor diameter ≥ 2 cm • Poor differentiation • Perineural invasion • Tumor invasion beyond subcutaneous fat