OBJECTIVETo study clinicopathologic features, immunohistochemical profile, diagnosis and differential diagnosis of childhood central nervous system primitive neuroectodermal tumors (CNS PNETs) with the features of ependymoblastoma and neuroblastoma.

METHODSThe clinical data, morphologic and immunohistochemical features were analyzed in 4 cases of pediatric CNS PNETs with features of ependymoblastoma and neuroblastoma. EnVision method immunohistochemistry was applied.

RESULTSFour patients including three boys and one girl presented at the age from 12 month to 4 years and three tumors located in cerebrum, one in brain stem. All tumors showed typical combined histological patterns of ependymoblastoma and neuroblastoma, demonstrating zones of true rosettes, occasional pseudovascular rosettes, and undifferentiated neuroepithelial cells in a prominent background of mature neuropils. There was focal expression of glial fibrillary acidic protein (GFAP) consistent with glial differentiation and epithelial membrane antigen (EMA) consistent with ependymal differentiation. Necrosis was seen in three cases and calcification was present in one case. Immunohistochemically, the rosettes and undifferentiated neuroepithelial cells were positive for vimentin, partially positive for GFAP and EMA but negative for synaptophysin. The tumor cells were also positive for synaptophysin in neuropils. The Ki-67 label index ranged from 20% to 60%.

CONCLUSIONSCNS PNETs with the features of ependymoblastoma and neuroblastoma is a rare tumor with poor prognosis. The tumor primarily occurs in childhood, especially infant and belongs to the family of embryonal tumors of the CNS. The morphologic, immunohistochemical and genetic features are important in differential diagnosis from other tumors of the CNS.