Characterization of testicular embryonic-type neuroectodermal tumor and embryonic-type neuroectodermal tissue admixed with mature neuro-glial tissue using a broad immunohistochemical panel

: Embryonic-type neuroectodermal tumor (ENT) is a somatic-type malignancy characterized by overgrowth of embryonic-type neuroectodermal tissue (EtNT). In germ cell tumors, EtNT is frequently intermingled with other components that may exhibit significant morphologic overlap [mature neuro-glial tissue (MNGT), nephroblastomatous tissues, and primitive endodermal-type glands]. Therefore, the quantification of EtNT (crucial for the diagnosis of ENT) can be challenging. In this study, we investigated the immunohistochemical profile of ENT, EtNT, and MNGT using a broad immunohistochemical panel. We found that SOX2 was the most sensitive marker for EtNT (100%), but it also stained MNGT (28.6%). GFAP and S100 were relatively sensitive (71.4%) and highly specific (GFAP 100%, S100 85.8%) for MNGT, whereas synaptophysin stained both. Combining our results with those of previous studies, we propose that a combination of SOX11, SOX2, GFAP, S100, AFP, villin, CDX2, PAX8, and nuclear WT1 may help to identify and quantify EtNT in germ cell tumors.