Primary tumor (T)

TX: The primary tumor cannot be assessed

T0: No tumor identified, but there is EBV‐positive cervical lymph node(s) involvement.

Tis: Carcinoma in situ

T1: Tumor confined to the nasopharynx, or extension to the oropharynx and/or the nasal cavity without parapharyngeal involvement

T2: Tumor with extension to the parapharyngeal space, and/or adjacent soft tissue involvement (medial pterygoid, lateral pterygoid, and prevertebral muscles)

T3: Tumor with infiltration of bony structures at the skull base, cervical vertebra, pterygoid structures, and/or paranasal sinuses

T4: Tumor with intracranial extension, involvement of cranial nerves, the hypopharynx, orbit, parotid gland, and/or extensive soft tissue infiltration beyond the lateral surface of the lateral pterygoid muscle

Abbreviations: AJCC, American Joint Committee on Cancer; T, tumor stage; N, nodal stage; M, metastatic stage; International Union Against Cancer Classification, UICC.