Unknown primary tumors of the head and neck (staging)

Last revised by Francis Deng on 8 Apr 2019

Unknown primary tumors of the head and neck staging refers to TNM staging of metastatic carcinomas in the head and neck region without an identifiable primary tumor. The typical scenario involves squamous cell carcinoma present in a cervical lymph node, no obvious primary source on clinical examination and imaging, and negative testing for both Epstein Barr virus (EBV) and human papillomavirus (HPV), which would otherwise be categorized as a T0 nasopharyngeal cancer or oropharyngeal (p16+) cancer, respectively. The following article reflects the 8th edition manual published by the American Joint Committee on Cancer (AJCC), which is used for staging starting January 1, 2018 1,2.

By definition, an occult primary tumor is designated T0 (no evidence of primary tumor).

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).

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 III
    • T0, N1, M0
  • stage IVA
    • T0, N2, M0
  • stage IVB
    • T0, N3, M0
  • stage IVC
    • T0, [Any N], M1

This staging system is new in the 8th edition, concurrent with elimination of the T0 category of each of the head and neck primary sites from the 7th edition except the HPV- and EBV-associated cancers. Salivary gland cancers also retain a T0 category due to their uniquely identifiable histology.

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