IDO overexpression was seen in higher levels in TNBC and HER2+ tumours than ER+/HER2- tumours (OR = 0.29 (0.08–1.08, p = 0.06) and OR = 0.76 (0.33–1.72, p = 0.51)), respectively [18]. The gene discussed is IDO1; the disease is neoplasm.