IDO1 and metastatic malignant neoplasm in the lymph nodes: Similarly, the positive rate of IDO expression in breast cancer patients with lymph nodes metastasis was significantly higher than those without lymph node metastasis, which were 76.00 and 50.00%, respectively (P < 0.05), while the mean MVD levels were 9.87 ± 1.89 and 8.81 ± 2.19, respectively (P < 0.05).