POU5F1 and seminoma: To annotate cell identities, we projected expression of sets of known cell type-specific marker genes and identified 8 major cell types, including seminoma (POU5F1+, TFAP2C+ and NANOG+), T cells (CD3D+ and CD3E+), B cells (CD79A+ and MZB1+), NK cells (CD160+ and FCGR3A+), endothelial cells (CDH5+), macrophage (CD68+ and LYZ+), plasmacytoid dendritic cells (pDCs; LILRA4+), smooth muscle cells (ACTA2+ and NOTCH3+) (Fig. 1b, e; see Supplementary Fig. 1e for additional markers).