Surprisingly, there was a reduction in ARG1 gene expression in tumour samples (2.50-fold decrease, mean LFC = −1.32 ± 0.30; p = 0.0008, 95% CI = −2.06 to −0.58), correlating to decreased levels of immunosuppressive ‘M2’ tumour-associated microglia/macrophages (TAMs). This evidence concerns the gene ARG1 and neoplasm.