SOX2 and neuroendocrine neoplasm: Molecular characterization by RT-qPCR (Figure 2, Table S2) and/or immunohistochemical (IHC) studies Figure 3 and Figures S16–S21, Table S3) of VP-MCC-like tumors confirmed the high-grade neuroendocrine tumor phenotype with expression of SOX2 and numerous neuroendocrine lineage gene as well as cytokeratin, including CK20.