Positive controls showed expected staining for OCT4 (Supplementary Figure 2A) and NANOG (Supplementary Figure 2C) in seminoma, SOX2 (Supplementary Figure 2B) in skin, KLF4 (Supplementary Figure 2D) in breast carcinoma, and c-MYC (Supplementary Figure 2E) in normal colon. This evidence concerns the gene POU5F1 and seminoma.