ERBB2 and neoplasm: Expression of CDK5 mRNA was assessed for associations with available clinicopathological data (Table 2); high CDK5 mRNA expression was significantly associated with higher tumour grade (χ2 = 12.898, df = 2, P = .002), luminal B PAM50 subtype (χ2 = 88.278, df = 5, P < .001), ER‐positive disease (χ2 = 8.588, df = 1, P = .003) and HER2‐negative disease (χ2 = 9.922, df = 1, P = .002).