In recent years, it has become clearthat the characteristics ofthe tumor microenvironment, including tumor hypoxia, contribute totumor progression and therapy resistance.36 Hypoxic areas are also known to have a decreased infiltration ofimmune cells.16 In B16ova tumors, we demonstratethat CAIX+ tumor areas contain a lower number of infiltratingleukocytes compared with CAIX– tumor areas. Here, CA9 is linked to neoplasm.