Primitive Neuroectodermal Tumors of Infancy and Childhood

We have reviewed the Children’s Hospital of Philadelphia’s experience with poorly undifferentiated small cell tumors of the central nervous system that are not medulloblastoma from 1968 through 1978. Using purely histologic criteria for diagnosis (i.e., small cell tumors with fields of deeply basophilic cells showing scant cytoplasm, some nuclear atypia, occasionally prominent nucleoli, endothelial hyperplasia, no secondary structures and in general reminiscent of germinal matrix tissue of the developing brain) we have been able to recognize 19 primitive neuroectodermal tumors (PNET) in children from 237 histologically verified brain tumors. This total excludes all unbiopsied tumors (e.g., thalamic tumors, brain stem tumors and some dominant parietal lobe lesions) which would increase the number of tumor patients seen by about 30%. Of these 19 PNETs, 11 were posterior fossa tumors and although they showed evidence of divergent differentiation were diagnosed in most instances as medulloblastoma. The remaining eight tumors included two pineal area lesions, which would qualify as pineoblastoma. Six met criteria to be diagnosed as PNETs as described by Hart and Earle[1] and recently again reviewed by Kosnik et al. [2]. Our incidence of PNET in 10 years is, therefore, 2.5% (6 of 237) but would be less (approximately 1.9%) if unbiopsied patients were included. A summary of the patient data is included below.