Brain tumors of childhood: nosological and diagnostic problems.

Brain tumors containing undifferentiated cells were selected from a series of 504 childhood brain tumors; 117 were analyzed. Most tumors were medulloblastomas, followed by cerebral neuroblastomas, pineocytomas-blastomas, ependymoblastomas, and polar spongioblastomas. Of each oncotype, the main histological features were evaluated, including differentiation and the most important prognostic factors. The terminology and different tumor entities are discussed in light of the recent PNET system. The usefulness of its application is evaluated in relation to prognosis.