Accordingly, immunohistochemical analyses of HIF1α and its target carbonic anhydrase IX (CAIX) indicate the presence of a hypoxic gradient in CLL LN with an inverse correlation between the intensity of CAIX staining and the distance from vessel, and highlight the proliferation centers as the areas with the lowest oxygen tension [3]. The gene discussed is HIF1A; the disease is B-cell chronic lymphocytic leukemia.