Tumors are classified according to the International Union Against Cancer (UICC) (3,4).
The T classification represents the extent of the primary tumor.
- T1 – small tumors ≤ 2 cm in largest diameter
- T2 – tumor 2–4 cm in largest diameter
- T3 – Tumor > 4 cm, < 6 cm
- T4 – Advanced tumors with invasion of neighboring organs, muscles, bone, and skin.
The N classification represents spreading to regional lymph nodes on the neck. The widest diameter is measured.
- N0 – no regional lymph node metastases
- N1 – single ipsilateral lymph node metastasis ≤ 3 cm
- a – single ipsilateral lymph node metastasis > 3 cm ≤ 6 cm
- b – multiple ipsilateral lymph node metastases ≤ 6 cm
- c – bilateral or contralateral lymph node metastases ≤ 6 cm
- N3 – ipsilateral lymph node metastases > 6 cm
The M classification represents distant metastases.
- M0 – no distance metastases
- M1 – distant metastases