Similarly, the IDO+SI in breast cancer with metastasis extended to N3 lymph nodes was significantly higher than those with metastasis limited to N2 and N1 lymph node or without lymph node metastasis, which were 28.35 ± 14.78%, 15.98 ± 7.14%, 11.42 ± 8.49%, and 10.29 ± 5.23%, respectively (P < 0.05). Here, IDO1 is linked to breast cancer.