Fig. 3. Principal component analysis (PCA) of tumour characteristics and lifestyle/patient-related risk factors and distribution of cases according to the resulting two main components (components 1 and 2).

a Loading plot of components 1 and 2 using the indicated variables (further details: Table 1). b Distribution of all cases (HPV₁₆-driven, HPV-negative and discordant HPV tests) without missing data (n = 598) according to the resulting main component scores. Selected cases mentioned in detail in Supplementary Table S4 are labelled. c Component-1 score efficiently separates HPV₁₆-driven and HPV-negative OPSCCs as indicated by the distribution plots next to the axis for both components. A separation border (dashed line) was defined at the central minimum. d Applying the separation border defined in (c) to cases with discordant HPV tests. The distribution plot of component 1 for HPV₁₆-driven and HPV-negative OPSCCs is indicated for comparison.