摘要：

目的 探讨第四脑室形成菊形团的胶质神经元肿瘤的临床病理学特征。方法与结果 女性患者，24 岁。临床表现为渐进性加重的头晕、运动障碍如行走不稳等症状。MRI 显示第四脑室扩张，其内可见长T₁、长T₂信号影，边界清晰，病灶内少许强化。手术切除第四脑室和菱形窝上方肿瘤，术中可见肿瘤分界清楚，分块切除，显微镜下未见肿瘤残留。光学显微镜观察肿瘤组织分别由神经元成分（“菊形团”或血管周围假“菊形团”样结构，中心呈均质淡染伴微囊形成）和神经胶质成分（毛细胞型星形细胞瘤样结构）构成，“菊形团”中心和血管周围假“菊形团”样结构表达突触素和少突胶质细胞转录因子2，毛细胞型星形细胞瘤样区域表达胶质纤维酸性蛋白，二者散在表达S-100 蛋白和神经元特异性烯醇化酶，Ki-67抗原标记指数为1.50% ~ 2.00%。结论 第四脑室形成菊形团的胶质神经元肿瘤为临床罕见的良性肿瘤，影像学呈边界清晰的实性或囊实性占位性病变；具有两种特征性组织学成分，免疫组织化学染色两种成分均表达突触素和胶质纤维酸性蛋白可提示诊断。

关键词: 脑室肿瘤, 神经元, 神经胶质, 第四脑室, 免疫组织化学, 病理学

Abstract:

Objective To explore the clinicopathological features of rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle.  Methods  The clinical manifestations, neuroimaging, histopathological and immunohistochemical features were analysed in one case of RGNT of the fourth ventricle, and related literatures were reviewed.  Results  A 24-year-old female presented with progressive dizziness under no obvious predisposing causes and dyskinesia such as stumbling. MRI revealed expansion of the fourth ventricle, and a mass with long T₁WI and T₂WI signal and clear boundary could be seen within the fourth ventricle. The border of tumor showed slight enhancement. At surgery, it was observed that the solitary tumor arised from the fourth ventricle and appeared well demarcated with rhomboid fossa. The tumor was blocking the aqueduct of sylvius before it was removed. Microscopically, the tumor exhibited both neuronic and astrocytic components. In the neuronic components, neurocytes formed neurocytic rosettes and perivascular pseudorosettes. At the center of the neurocytic rosettes, there was an eosinophilic core and some region consisted of microcysts. While the astrocytic components of the tumor revealed typical pilocytic astrocytoma structure. The center of neuronic rosettes and perivascular pseudorosettes displayed strong positive staining with synaptophysin (Syn) and oligodendrocytes transcription factor-2 (Olig-2). The astrocytic components showed positive immunostaining of glial fibrillary acidic protein (GFAP). There were focal and partial positive immunostaining of neuron-specific enolase (NSE) in both components of the tumor. The Ki-67 labeling index was 1.50%-2.00% in two components.  Conclusions  Rosette-forming glioneuronal tumor of the fourth ventricle is an unusual neuronal and mixed neuronal-glial tumors. The imaging examination showed solid or mixed solid-cystic mass at the fourth ventricle with well demarcated border. The lesion has two characteristic components and the distinctive immunostaining of GFAP and Syn expression will help the differential diagnosis.

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