Tumor protein p53 could not be pooled because definitions for positivity were too heterogeneous, ranging from a “clear brown color, regardless of the staining intensity” and “>5% staining” to “≥50% nuclear/cytoplasmic staining.”66, 67, 70, 77 When looking at least at exon 5‐8 (coding the DNA binding portion of p53 and containing >90% of the mutations described in HNSCC), TP53 mutations were found in 35% of the 235 nonsmokers presented in the six included studies.54 This evidence concerns the gene TP53 and head and neck squamous cell carcinoma.