In the patients with SCLC, higher expression of CDK5 was found in female (100 %, 5/5) and lymph node metastasis (76.9 %, 10/13) compared with that in male (47.6 %, 10/21, P = 0.037) and without lymph node metastasis (30 %, 3/10, P = 0.028, Table 5), respectively. Here, CDK5 is linked to metastatic malignant neoplasm in the lymph nodes.