Table 1. Primary Tumor (T)a
| TX | Primary tumor cannot be assessed. |
| T0 | No evidence of primary tumor. |
| Tis | Carcinoma in situ. |
| T1 | Tumor ≤2 cm in greatest dimension. |
| T2 | Tumor >2 cm but ≤4 cm in greatest dimension. |
| T3 | Tumor >4 cm in greatest dimension. |
| T4a | Moderately advanced local disease.b |
| (Lip) Tumor invades through cortical bone, inferior alveolar nerve, floor of mouth, or skin of face, that is, chin or nose. |
| (Oral cavity) Tumor invades adjacent structures only (e.g., through cortical bone [mandible or maxilla] into deep [extrinsic] muscle of tongue [genioglossus, hyoglossus, palatoglossus, and styloglossus], maxillary sinus, or skin of face). |
| T4b | Very advanced local disease. |
| Tumor invades masticator space, pterygoid plates, or skull base and/or encases internal carotid artery. |
| aReprinted with permission from AJCC: Lip and oral cavity. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 29-40. |
| bSuperficial erosion alone of bone/tooth socket by gingival primary is not sufficient to classify a tumor as T4. |
