ABSTRACT
Embryonal tumors, predominantly arising in pediatric patients, are categorized in the most recent World Health Organization (WHO) classification as lesions that demonstrate an undifferentiated round cell tumor background and divergent patterns of differentiation (1) Tumor types within this classification include medulloblastoma-the most common form of embryonal tumor, supratentorial primitive neuroectodermal tumor (sPNET), medulloepithelioma, ependymoblastoma, medullomyoblastoma, and melanotic medulloblastoma (Table 1) (1). The atypical teratoid/rhabdoid tumor (ATRT), a newly categorized lesion occurring primarily in very young children, is also classified as an embryonal tumor. The pineoblastoma, histologically similar to the medulloblastoma and sPNET, has been categorized by the WHO as a
pineal parenchymal tumor. Although embryonal tumors share common light microscopy features, they seem to evolve by different genetic pathways (2). Principles of management for embryonal tumors are relatively similar as all are aggressive and have a proclivity to disseminate the central nervous system early in the course of illness. However, the intensity of therapy required for disease control and prognosis is variable within and among tumor subtypes, and is dependent not only upon the histology of the embryonal tumor, but also its molecular genetic make up, the age of the patient, and possibly the location of the tumor within the nervous system.
