An infant case of intracranial peripheral-type primitive neuroectodermal tumor with long-term survival.

Supratentorial primitive neuroectodermal tumors (S-PNET) that develop in children have recently been classified into two types: central-type PNET (C-PNET), which has been reported over the years, and peripheral-type PNET (P-PNET), which develops intracranially and was referred to as Ewing's sarcoma in the past. P-PNET is fundamentally a malignant tumor, but the patient reported here represents a case of long-term survival from onset without recurrence. At the age of 21 months, a male infant developed a cranial bone deformity and symptoms of high intracranial pressure. A CT scan revealed a cystic tumor attaching to the falx, and cyst drainage operation was immediately performed. The intracranial tumor was then resected. The tumor was an intradural extramedullary tumor, and it was totally excised with the falx attachment. The tumor was initially diagnosed as a neuroblastoma, and postoperative treatment consisted of administration of radiotherapy and chemotherapy using cyclophosphamide and vincristine. Twenty years have now passed without any recurrence. Recent repeated performance of histopathological analysis resulted in a diagnosis of P-PNET. In recent years, studies in molecular biology have demonstrated that P-PNET involves the EWS-FLI1 chimeric gene, and immunohistochemical staining has shown P-PNET to be MIC2 positive. P-PNET also differs from C-PNET with regard to prognosis, and for this reason it is believed that P-PNET and C-PNET should be considered separate entities. That is, in spite of the fact that P-PNET is a malignant tumor, patient survival can be comparatively long. Because P-PNET originates intracranially, it is fundamentally an intradural extramedullary tumor. For this reason, treatment should consist of surgical excision that is as complete as possible, followed by appropriate radiotherapy and chemotherapy. This approach can be expected to result in the patient's long-term survival.