JCHAIN and seminoma: Using canonical cell type markers, these populations were annotated as follows: seminoma cells (NANOG, POU5F1, SOX17), T cells (CD3D, CD3E, CD3G), myeloid cells (LYZ, FCER1G, CD14), plasma/B cells (MZB1, JCHAIN, IGHG1), endothelial cells (VWF, CD34, CLDN5), plasmacytoid dendritic cells (IRF7, IRF8, PLAC8), myoid cells (ACTA2, MYL9, MYLK), fibroblasts (COL3A1, COL1A2, DCN), spermatogonia (SYCP3, DMRT1), and spermatozoa (SPACA1, ACRV1, AKAP4) (Fig. 1c).