Peripheral primitive neuroectodermal tumor (peripheral neuroepithelioma) in children. A review of the St. Jude experience and controversies in diagnosis and management

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Abstract
All patients diagnosed with primitive neuroectodermal tumor (PNET) and extraosseous Ewing's sarcoma in one institution between 1962 and 1987 were reviewed. Of the 26 cases studied, 16 had been diagnosed originally as PNETs, seven tumors were rediagnosed as PNET or EOE by histologic review, and three tumors had an original diagnosis of extraosseous Ewing's sarcoma. To determine whether these diagnoses determine a group of tumors with unique biologic behavior and identifiable pathologic characteristics, clinical and treatment response data were compiled, and electron microscopic and immunohistochemical studies were done for those patients with adequate samples. With combined modality therapy, this group achieved a substantially shorter disease control interval than patients with disseminated osseous Ewing's sarcoma or disseminated neuroblastoma—10.8 months versus 17 months and 16 months, respectively. The pattern of relapse and distant spread also differed among these tumor types. Immunohistochemical studies (for example, neuron-specific enolase and β2 microglobulin) were helpful in confirming the diagnosis but were not definitive in themselves. Tentative diagnostic criteria are proposed for use in studies designed to provide further information on the nature and treatment of PNET. Some of the controversies regarding diagnosis are discussed. The authors propose a uniform approach to treatment of extraosseous Ewing's sarcoma and PNET in order to try to clarify their relation.