MYCN and neoplasm: Early passage PDOX tumors were evaluated histologically and compared to their corresponding patient tumors by Hematoxylin and Eosin (H&E) staining of tumor sections, by immunohistochemistry (IHC) to detect characteristic markers of each tumor entity and subgroup, and fluorescence in situ hybridization (FISH) for relevant genetic alterations (i.e., MYC and MYCN amplification in MB, C19MC amplification in ETMR).