PLK4 and neoplasm: Notably, we found that the expression of PLK4 was markedly correlated with Ki67 expression level (p < 0.001), tumor size (p = 0.041), TMN stage (p = 0.002), CEA (p = 0.016), lymph node metastasis status (p = 0.012) and tumor capsule status (p = 0.001) (Table 3).