Table 2.

Primary tumor (T)*.

Tx	Primary tumor cannot be assessed
T0	No evidence of primary tumor
Tis	Carcinoma in situ
T1	Carcinoma less than 2 cm in greatest dimension, with less than 2 high risk features**
T2	Carcinoma greater than 2 cm in greatest dimension, Or Tumor of any size with at least 2 high risk features**
T3	Tumor invasion of the maxilla, mandible, orbit, or temporal bone
T4	Tumor invasion of the skeleton (appendicular or axial) or with perineural involvement of the skull base

*Excludes cutaneous SCC of the eyelid.

**High-risk features for the primary tumor (T) staging:

Depth/invasion: >2 mm thickness, Clark level ≥IV, Perineural invasion.

Anatomic location: Primary site ear, Primary site non-hair-bearing lip.

Differentiation: Poorly differentiated or undifferentiated.

From the AJCC 7th edition “Cutaneous Squamous Cell Carcinoma and Other Cutaneous Carcinomas”.