PDPN and leukoplakia: Table 1 summarizes clinical and biochemical characteristics with pairwise comparisons. Age, smoking, alcohol use, CRP, glucose, ALT, AST, and both serum and salivary PDPN levels increased progressively from control → leukoplakia → cancer (all p < 0.05). PDPN levels were highest in the cancer group: Serum: 3.5 ± 0.9 ng/mL, Saliva: 2.6 ± 0.7 ng/mL (Figure 2 and Figure 3).