The epithelial component showed focal staining with CK7 and nonspecific staining with synaptophysin and CD99. Chromogranin was negative, excluding the presence of neuroendocrine differentiation. Negativity for calretinin excluded a biphasic mesothelioma, negativity for SALL4 excluded a germ cell tumor, and negative staining with TLE1 and BCL2 had excluded the possibility of synovial sarcoma (Figure 3). The gene discussed is CD99; the disease is testicular germ cell tumor.