FGF2 and central nervous system cancer: In line with our findings, previous cohort studies found no association between glioma risk and levels of IL‐13, TNF‐α, CXCL13, MIP‐1α, MIP‐1β, fractalkine, FGF2, TGF‐α, sCD23, sCD27 and sCD30.10, 11, 12