One likely explanation of this phenomenon is consistent with the observation that different regulation pathways of HIF-1α overexpression exist in breast cancer: (1) hypoxia induced, perinecrotic HIF-1α overexpression with strong expression of hypoxia associated genes, which is associated with a poor prognosis; and (2) diffuse HIF-1α overexpression lacking major hypoxia associated downstream effects, resulting in a more favorable prognosis [35, 36]. This evidence concerns the gene HIF1A and breast cancer.