CDK5 and undifferentiated carcinoma: Higher CDK5-positive expression was also found in the subgroups of NSCLCs including adenocarcinoma (P = 0.003), squamous cell carcinoma (P = 0.003), adenosquamous carcinoma (P = 0.001), and undifferentiated carcinoma (P = 0.02), than that in the normal lung tissue.