Immunohistochemical staining of tumor sections with antibodies against pRb and phosphorylated Rb (ppRb) displayed high levels of pRb and ppRb in both RB1+/+ and RB1+/− tumors with MYCN amplification compared to no expression of these proteins in a classic RB1−/−, MYCN‐low tumor. This evidence concerns the gene RB1 and neoplasm.