Gliomas are characterized by myeloid skewing and IL-6-associated inflammation, CNS lymphomas by IL-10/CXCL13-driven B-cell-supportive niches, brain metastases by primary tumor-imprinted inflammatory signatures, and leptomeningeal metastases by profound macrophage dominance and complement-mediated immune reprogramming. The gene discussed is IL10; the disease is primary central nervous system lymphoma.