摘要目的 探讨小儿以室管膜母细胞瘤和神经母细胞瘤成分为主的中枢神经系统原始神经外胚层肿瘤(PNET)的临床病理特点、免疫表型、诊断和鉴别诊断.方法 回顾性复习4例以室管膜母细胞瘤和神经母细胞瘤成分为主的中枢神经系统PNET的临床资料、镜下形态及免疫表型特点,免疫组织化学采用EnVision法.结果 4例均为婴幼儿,年龄最小12个月,最大4岁;男3例,女1例;3例肿瘤位于大脑,1例位于脑干.显微镜下4例肿瘤均具有特征性的组织学改变,即同时具有室管膜母细胞瘤和神经母细胞瘤的特征,部分区域肿瘤细胞围绕中空的腔隙排列成真菊形团,也可伴血管周围假菊形团;部分区域在丰富的神经毡背景中可见大量原始未分化的神经上皮细胞.3例伴有神经胶质分化,显示胶质纤维酸性蛋白(GFAP)部分或灶性阳性;3例伴室管膜分化,显示上皮细胞膜抗原(EMA)部分阳性.4例中有3例伴有不同程度的坏死,1例伴沙砾体样钙化.免疫组织化学染色显示围成菊形团的肿瘤细胞和原始神经上皮细胞成分波形蛋白阳性,GFAP部分或灶性阳性,EMA部分阳性,突触素阴性;神经毡区域突触素阳性;Ki-67阳性指数20％ ～ 60％.结论 以室管膜母细胞瘤和神经母细胞瘤成分为主的中枢神经系统PNET是发生于儿童尤其是婴幼儿的中枢神经系统胚胎性肿瘤,非常罕见且预后极差,其特征性的组织形态学表现、免疫组织化学表型及遗传学改变是与其他中枢神经系统肿瘤鉴别的关键.

abstractsObjective To 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.Methods The 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.Results Four 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％.Conclusions CNS 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.