GAB1 and ependymoma: Newly introduced stains included stains used for differentiation between cell lineages (Olig2), surrogate markers for molecular alterations (IDH1 R132H, ATRX), markers of specific tumor types (Lin28 for ETMR and L1CAM for supratentorial ependymoma, RELA/ZFTA fusion-positive), and markers for tumor subtyping (including GAB1 for SHH-activated tumor and H3 K27me3 for ependymoma, posterior fossa-A/posterior fossa-B distinction).