目的 探讨毛细胞型星形细胞瘤 的MR特点和病理学特征。方法 回顾性分 析17例毛细胞型星形细胞瘤的术后病理、 术前MR资料。结果 17例毛细胞型星形细 胞瘤中，发生于幕上5例，幕下12例。囊 结节型共11例，实质型4例，囊肿型2例。 MR平扫肿瘤境界清楚，无明显瘤周水肿， 除1例瘤内出血外其余肿瘤的囊液部分均 显示为长T1、长T2信号；实性部分或瘤结 节T1WI呈稍低信号,T2WI稍高信号,增强后 明显强化。囊壁光滑、强化或不明显强 化。显微镜下瘤组织内致密、疏松区双相 交替，瘤细胞呈细长梭形，致密区见数量 不等Rosenthal纤维，疏松区有微囊样结 构、嗜酸性小体形成；肿瘤免疫组化GFAP 阳性。结论 毛细胞型星形细胞瘤MR影像 表现和病理组织学具有特征性，把握其病 理特点有助于术前影像诊断。

Objective To investigate MR features and pathological characteristics of the pilocytic astrocytoma (PA). Methods MR imaging and post-operative pathological data of 17 patients with PA were analyzed retrospectively. Results Among these 17 cases of PA, the tumors were supratentorial in 5 and infratentorial in 12. 11 cases were large cystic with nodule type, 4 cases were solid mass type, and 2 cases were purely cystic type．In MR image, lesions were sharply demarcated with 1ittle or no surrounding edema.The cystic liquid exhibited long T1 and long T2 signal except 1 case of intratumoral hemorrhage. The solid part or nodule showed slightly low signal on T1WI, slightly high signal intensity on T2WI and could be significantly enhanced. The wall of cyst was smooth, could be significantly enhanced or non-enhanced. Microscopical study: PA characteristically contained alternative densely packed areas and loosly packed areas. The tumor cells had elongated hair-like cytoplasmic processes. Rosenthal fibels varying in amount from a few to substantial could be found and were particularly common in the fibrillary area. The loose tissues were composed of minute vacuoles and microcysts. Tumor cells expressed GFAP. Conclusion Accurate comprehension of MR features and pathological characteristics of the PA is beneficial for pro-operative daignosis．