Methods
Search strategy
Bibliographic databases Pubmed, Medline and Embase search engines were searched to identify studies from inception to October 2021. Search terms used included “cancer of unknown primary” AND “tonsillectomy” OR “tongue base mucosectomy” OR “lingual tonsillectomy”, “unknown primary tumour AND squamous cell carcinoma of head and neck”, “oropharyngeal cancer AND biopsy”.
Inclusion and exclusion criteria
All primary human studies were included regardless of study type. Exclusion criteria included individual case reports, non-original studies, studies with non-extractable data, or including large proportions of non-squamous cell carcinoma patients.
Within the literature, variability exists as to when individual authors’ make a HNSCCUP diagnosis 8. The heterogeneity results from the extent of the preceding workup prior to diagnosis. No meaningful adjustments could be made to standardise the workup and so no exclusions were made on this basis.
Study selection
The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed9 Titles and abstracts were independently screened by two reviewers (NK/RT). Disagreements were resolved by discussion with the senior authors (SL).