Table 2.

Important differences between AJCC TNM 7th and 8th editions

TNM stage	p16–	p16+
T staging	Same as AJCC 7th edn	Tis: not included T0: only for p16+ metastatic lymph nodes T4: formerly divided into T4a and T4b, now unified into a single category
Clinical N staging	N3: nodes >6 cm in diameter further subdivided into N3a and N3b on the basis of the absence (former) or presence (latter) of extranodal extension	N1: ipsilateral lymph nodes ≤6 cm N2: bilateral or contralateral nodes ≤6 cm no N2 subcategories N3: nodes >6 cm
Pathological N staging	Same as AJCC 7th edn	N1: involvement of ≤4 metastatic lymph nodes N2: >4 metastatic nodes N3: removed
HPV status	p16 testing; tumours with at least moderate staining intensity and diffuse staining (≥75% of tumour cells) classified as probable HPV-associated aetiology on the basis of p16 positivity

See ref.²⁴⁴. AJCC, American Joint Committee on Cancer; HPV, human papillomavirus.