MIHC staining revealed that SPP1 was substantially colocalized with CD68+ cells but barely colocalized with CD4+ T cells, CD8+ T cells or B cells and that SPP1 was more highly expressed in macrophages derived from HNSCC tumor tissues compared with those derived from adjacent normal tissues (Fig. 2D, E, Supplementary Fig. S2D). Here, CD68 is linked to neoplasm.