RB1 and neoplasm: Genomic studies of MCCs, especially MCPyV-negative tumors, have identified chromosomal copy number variations (CNVs) and frequent mutations in tumor suppressor genes such as TP53 and RB1 (retinoblastoma 1)22,23, several oncogenes including HRAS, KRAS24,25, and genes encoding phosphatidylinositide-3-kinase (PI3K)/AKT/mTOR pathway26–28.