Purpose To explore the clinicopathologic characteristics and differential diagnosis of pilomyxoid astrocytoma( PMA ). Methods The clinical data of three cases of PMA and examined the histopathologic and immunohistochemical ( using EnVision-plus kit )features were reported. The ultrastructural features were examined in one of these cases. Results Three PMA occurred in female patients at the age of 13 years,4 years and 17 years, and the tumor were located in the right thalamus, right temporal lobe/basal ganglia and hypothalamic/chiasmatic region, respectively. On histology , the tumor was composed of bipolar spindle cells loosely setting in a mucinous background. In some areas, the tumor cells displayed an angiocentric pattern. Pleomorphism of the tumor cells was not significant. Mitotic figures were rare. There was a marked proliferation of vessels within the tumor. There was hemorrhage in one case. Eosinophilic granular bodies and focal necrosis were seen in one case, and the hiphasic pattern and Rosenthal fibers were not found in all the three cases. Immunophenotyping showed that the tumor cells of all cases were diffusely positive for GFAP. vimentin,S-100 and Olig-2 ,while negative for CKpan,EMA, NF, CgA,Neu-N and p53. The tumor cells of one case were focally positive for Syn. The. tumor cell of PMA contained neuroendocrine granule-like particles besides the characteristics of tanycyte under electron microscopy. Conclusion PMA is a subtype of pilocytic astrocytoma ( PA ). Compared to the classic type PA,it has the unique histological characteristics.and is more aggressive. Therefore , we should strengthen cognition of this tumor.%目的 探讨毛细胞黏液样星形细胞瘤(pilomyxoid astrocytoma,PMA)的临床病理特点及鉴别诊断.方法 报道3例PMA患者的临床资料,并对其进行组织学观察及免疫组化(EnVision-plus法)标记,其中1例行电镜观察.结果 本组PMA均为女性,年龄分别为13岁、4岁和17岁.肿瘤分别位于右侧丘脑、右侧颞叶基底节区及下丘脑/视交叉区.镜下见双极性的梭形瘤细胞呈星网状散在分布于黏液背景中,部分区域呈血管中心性生长,瘤细胞异型性小,核分裂象偶见,间质血管增生明显.1例见大片出血,1例见少许嗜酸性颗粒小体及小灶坏死,3例PMA均未见双相性结构及Rosenthal纤维.免疫组化标记示瘤细胞表达GFAP、vimentin、S-100及Olig-2,而CKpan、EMA、NF、CgA、Neu-N、p53均呈阴性表达,Syn有2例局灶阳性,Ki-67阳性率为1%～2%.仅有的1例电镜表现除具有伸长细胞特征外,胞质内还可见神经内分泌样颗粒.结论 PMA为毛细胞星形细胞瘤(pilocytic astrocytoma,PA)的亚型,与经典PA相比,具有独特的组织学特征,并具有更强的侵袭性,故应加强对其的认识.
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