CD163 Dominance Within Macrophages/Microglia Reflects a Favorable Prognosis in Patients With Glioblastoma

Glioblastoma is the most common primary malignant central nervous system (CNS) tumor; however, its microenvironment, including tumor‐associated microglia/macrophages (TAMs), is not fully understood. Although ionized calcium‐binding adaptor molecule 1 (IBA‐1) is expressed in various microglial phenotypes in the healthy human brain, CD163 is a marker of activated/phagocytic microglia. Tissues from 34 patients with glioblastoma were analyzed, and 17.6% of cases were CD163‐dominant. CD163‐dominant patients showed better overall survival than IBA‐1‐dominant patients ( p = 0.019). CD163 dominance was identified as an independent prognostic factor for overall survival (hazard ratio [HR], 0.17; p = 0.011). Compared with the IBA‐1‐dominant group, CD163‐dominant tumors showed more CD4‐positive cell infiltration ( p = 0.005), fewer ameboid TAMs ( p = 0.021), and fewer non‐microvascular proliferation (non‐MVP) vessels ( p = 0.012). No significant differences were found in patient characteristics, such as age, sex, tumor location, or extent of resection. The CD163‐to‐IBA‐1 ratio of TAMs is a significant independent prognostic factor in glioblastoma, suggesting that the activation status of these cells and their interactions with the vascular endothelium and T cells influence tumor progression. These findings highlight TAMs as potential therapeutic targets for glioblastoma.