SPP1 and central nervous system cancer: We then performed clustering on the TAM subsets from the 17 cross-grade glioma patients and found three major TAM subsets with distinguished expression of CCL3, AIF1, and SPP1 respectively, the three subsets also share most of the marker genes with the previously identified TAMs in grade 2 glioma (Fig. 4h, i and Additional file 8: Table S4).