Inconsistent results were obtained for macrophages: PER1 expression showed different correlations with gene markers of M1 macrophages (e.g., PTGS2 and IRF5) and those of M2 macrophages (e.g., CD163, VSIG4, and MS4A4A), which may explain the potential ability of PER1 to regulate tumor-associated macrophages. This evidence concerns the gene MS4A4A and neoplasm.