PRIMITIVE NEUROECTODERMAL TUMORS OF THE CENTRAL-NERVOUS-SYSTEM

Controversial issues relating to the pathobiology and classification o f central nervous system primitive neuroectodermal tumors (PNETs) have plagued neuropathologists for more than 70 years Hypotheses advanced in the mid-1920's have remained as fixed concepts in contemporary lite rature, largely consequent to repetitious support by a small number of neuropathologists despite a growing body of information discrediting these ideas from neuroembryologists, oncologists, neuroscientists and pathologists. Attention has largely focused upon PNETs arising in the cerebellum (commonly known as medulloblastomas [MBs]), because about 8 0% of central nervous system (CNS) PNETs originate in this site. It ha s been asserted that the 20% which do not are biologically different, although most individuals agree that the histological features of PNET s that occur in different sites throughout the CNS are indistinguishab le from those growing in the cerebellum. The historical aspects of thi s controversy are examined in the face of evidence that there is, in f act, a unique class of CNS tumors which should appropriately be regard ed as primitive neuroectodermal in nature. Specifically, a number of d ifferent approaches to the problem have yielded data supporting this h ypothesis. These approaches include the identification of patterns of expression among a variety of cellular antigens (demonstrated by the u se of immunopathological techniques), molecular analyses of cell lines derived from these tumors, experimental production of PNETs and molec ular genetic analyses. Differences of opinion among surgeons, oncologi sts and radiotherapists are typically resolved by conducting cooperati ve studies of patients with these tumors who are diagnosed and treated at multiple centers.