CDK4 and metastatic malignant neoplasm in the lymph nodes: There was no significant difference between CDK4 amplification and CDK4 non-amplification group regarding sex, age, grade, invasive depth, vessel and nerve invasions, lymph node metastasis, anatomic site, smoking, and clinical stage, which is in line with the conclusion that no significant associations were found between CDK4 gene amplification and patient’s age, tumor size, and lymph node status in breast cancer (An et al., 1999).