ABSTRACT
Embryonal tumors are biologically heterogeneous lesions that are characterized by the presence of hyperchromatic cells with little cytoplasm, high mitotic activity and apparent cellular transformation; and that are disseminated throughout the nervous system via cerebrospinal fluid pathways. Central nervous system (CNS) primitive neuroectodermal tumor (PNET) (often referred to as noncerebellar PNET) may arise in the cerebral hemispheres, brainstem, or spinal cord and contains undifferentiated or poorly differentiated neuroepithelial cells with the capacity for differentiation along neuronal, glial, or other lineages. MicroRNAs are small, endogenously expressed nonprotein coding RNAs that interact with target messenger RNAs and regulate a broad range of cellular and developmental processes. Embryonal tumor with multilayered rosettes is usually a large, demarcated, solid mass featuring patchy or no contrast enhancement, edema, significant mass effect, occasional cystic components, and microcalcifications. Histologically, the tumor contains small to medium-sized cells with scanty perinuclear cytoplasm and hyperchromatic nuclei and shows divergent differentiation along neuronal, astrocytic, muscular, or melanocytic lines.
