MKI67 and leukoplakia: Kaplan–Meier analyses charting the cumulative probability of recurrence of leukoplakia showed a trend that the high expression group of all four biomarkers by itself was associated with recurrence after surgical excisions (Ki-67; p = 0.72, p53; p = 0.27, p63; p = 0.11 and PDPN; p = 0.23; Fig. 3).