Oropharyngeal (p16-negative) cancer (staging)

Oropharyngeal (p16-) cancer staging refers to TNM staging of carcinomas originating in the oropharynx that are not human papillomavirus (HPV)-associated. This system most commonly pertains to squamous cell carcinomas that tested negative for p16, an immunohistochemical proxy for HPV infection, or were not tested. Also included are minor salivary cancers and neuroendocrine carcinomas, in which p16 assessment is not required or contributory. The following article reflects the 8^th edition of the classification by the American Joint Committee on Cancer (AJCC) and Union for International Cancer Control (UICC), published in 2017 ^1-4.

Primary tumor (T)

• TX: primary tumor cannot be assessed

• Tis: carcinoma in situ

• T1: tumor ≤2 cm in greatest dimension

• T2: tumor >2 cm and ≤4 cm

• T3

  • tumor >4 cm, or

  • tumor extension to lingual surface of epiglottis

• T4: moderately or very advanced

  • T4a: moderately advanced local disease in which tumor invades any of the following:

    • larynx (except lingual surface of epiglottis)

    • extrinsic muscles of the tongue* 

    • medial pterygoid muscle

    • hard palate

    • mandible

  • T4b: very advanced local disease in which tumor encases carotid artery or invades any of the following:

    • lateral pterygoid muscle

    • pterygoid plates

    • lateral nasopharynx

    • skull base

*Note: According to the AJCC, involvement of the palatoglossus muscle within the oropharynx does not change the T category and this criterion mainly denotes invasion "anteriorly to the extrinsic muscles of the tongue in the floor of the mouth" ¹. According to the UICC, this criterion is defined as "deep/extrinsic muscle of tongue (genioglossus, hyoglossus, palatoglossus, and styloglossus)" ⁴. The application of this criterion is controversial because only the genioglossus is deep among the extrinsic tongue muscles ⁵.

Regional lymph node (N)

Regional nodal status is defined the same as for most other cancers of the head and neck. See the main article, cervical lymph node (staging).

Distant metastases (M)

The terms pM0 and MX are not valid TNM categories. The following categories may be used:

• cM0: no evidence of metastases

• cM1: distant metastasis

• pM1: distant metastasis, microscopically confirmed

Stage groups

The prognostic stage groups are defined the same as for most other cancers of the head and neck:

• stage 0

  • Tis, N0, M0

• stage I

  • T1, N0, M0

• stage II

  • T2, N0, M0

• stage III

  • T3, N0, M0

  • [T1, T2, T3], N1, M0

• stage IVA

  • T4a, [N0, N1], M0

  • [T1, T2, T3, T4a], N2, M0

• stage IVB

  • [Any T], N3, M0

  • T4b, [Any N], M0

• stage IVC

  • [Any T], [Any N], M1

Changes since prior versions

The 8th edition staging system separated HPV-associated and non-HPV-associated oropharyngeal cancers ³. Otherwise, the T category definitions did not change from the 7th edition staging system. Nodal staging was changed, as with other head and neck sites, to emphasize extranodal extension.

See also

• HPV-mediated (p16+) oropharyngeal cancer staging

• WHO classification of head and neck tumors

• cervical lymph node levels

• cervical lymph node staging