儿童毛细胞黏液样星形细胞瘤的影像与病理特征研究

目的　探讨儿童毛细胞黏液样星形细胞瘤（PMA）的影像特征及其与病理学改变的关系。方法　回顾性分析2010年10月至2018年6月首都医科大学附属北京天坛医院收治的20例儿童颅内PMA患者的临床资料、CT和磁共振成像（MRI）影像表现以及病理和免疫组织化学结果。结果　20例儿童PMA患者中，男15例，女5例；肿瘤位于幕下小脑半球10例，幕上大脑半球5例，视交叉-下丘脑4例，三脑室内1例。在CT图像上，PMA表现为低密度10例；在MRI图像上，肿瘤呈混杂信号11例，T1WI低信号7例，T2WI高信号7例，DWI未见弥散受限12例，MRI增强扫描表现为不均匀强化17例；肿瘤边界清楚18例，发生囊变16例，瘤周水肿11例。组织病理学检查可见双极性梭形细胞，以血管为中心生长，间质内含有大量黏液，缺乏Rosenthal纤维。结论　儿童PMA具有较为特征性的影像表现和低度恶性的肿瘤特征，肿瘤不均质性、边界清楚、边缘囊变和不均匀强化是PMA的特征性表现，CT和MRI可为儿童PMA的术前诊断、临床治疗和预后评估提供参考。

Imaging and pathological features of pilomyxoid astrocytoma in children

Objective　To investigate the imaging characteristics and their relationship with histopathological changes of pilomyxoid astrocytomas（PMA） in children. Methods　The CT and MRI findings as well as clinical data of 20 pediatric patients with PMA admitted to Beijing Tiantan Hospital，Capital Medical University between October 2010 and June 2018 were analyzed retrospectively，and their clinical features，pathological and immunohistochemical results were also analyzed. Results　There were 15 males and 5 females in total 20 patients with PMA. Tumors were located at cerebellar hemisphere in 10，cerebral hemisphere in 5，chiasmatic-hypothalamic region in 4 and at the third ventricle in 1. Of 20 patients with PMA，10 presented hypodense on CT images，11 showed mixed signal intensity on both T1 and T2 weighted images on MRI，7 demonstrated hypointensity on T1WI and 7 had hyperintensity on T2WI. Absence of diffusion restriction were noticed in 12 tumors. The tumors showed significant inhomogeneous enhancement in 17 cases under MRI enhanced screening. The cases of neoplasm clear margin，necrosis inside tumors and peritumor edema were 18，16 and 11，respectively. Histopathologically，PMA was characterized by the presence of bipolar spindle cells，angiocentric arrangement，prominent myxoid background and the lack of Rosenthal fibers. Conclusion　The pediatric PMA has low-grade tumor features and characteristic imaging features. There are several imaging features which are relatively specific for PMA on CT and MR images，such as heterogeneous texture，clear border，cystic changes of edge and inhomogeneous enhancement. CT and MRI may provide valuable information for preoperative diagnosis，clinical treatment and prognostic evaluation in patients with PMA.