Both ipsilateral and any breast cancer recurrence were more frequent in women with HIF-1α-positive primary tumours (hazard ratio, HR0–5 yrs1.9 [1.3–2.9], p = 0.003 and HR0–5 yrs = 2.0 [1.5–2.8], p < 0.0001). The gene discussed is HIF1A; the disease is neoplasm.