儿童颅内毛细胞型星形细胞瘤的误诊原因分析

Analysis of Misdiagnosed Intracranial Pilocytic Astrocytomas in Children

目的探讨儿童颅内毛细胞型星形细胞瘤(PA)的影像学诊断及分析误诊原因。方法回顾性分析36例经手术病理证实为PA而术前误诊为其他肿瘤的病例,男性23例,女13例,分析其CT和MRI表现,总结误诊原因。结果36例PA中,14例位于小脑,7例位于鞍区,6例位于大脑,5例位于脑干,3例位于松果体区,1例多发病灶。其中5例(13.9%)见肿瘤内钙化,3例(8.3%)见肿瘤内出血,21例(58.3%)表现为各种不典型强化,2例(5.6%)出现脑脊液播散。11例的Cho/NAA平均值为2.53±0.94,其中9例Cho/NAA比值>2,4例可见Lac峰。本组35例(97.2%)DWI呈等、低信号。结论肿瘤内钙化、出血,不典型强化方式,软脑膜播散,多发病灶以及与恶性肿瘤相似的MRS表现是PA的误诊原因。DWI呈等或低信号,肿瘤边界清楚,无或轻度瘤周水肿则支持PA的诊断。

Objective In order to evaluate the reasons of mistaken diagnosis, the imaging features of the misdiagnosed intracranial pilocytic astrocytoma in children were analyzed. Methods We collected 36 cases that were pathologically proven to be misdiagnoses. Among them 23 were boys and 13 were girls. The results of CT and MRI were retrospectively reviewed to analyse the causes of the misdiagnoses. Results In the group, 14 cases were in the cerebellum, 7 in the sad- dle area, 6 in the cerebrum, 5 in the brain stem, 3 in the pineal region and 1 was polynesic. In 36 cases, 5/36（ 13.9% ） had calcification, 5/36（8.3% ） had hemorrhage, 21/36（58.3% ） had atypical enhancement and 2/36（5.6% ） had CSF dissemination. The Cho/NAA mean for the 11 cases was 2.53 ± 0.94. There were 9 cases with Cho/NAA 〉 2, 4 cases with Lac peaks. 35/36 （97.2%） tumors were isoto-hypointensity on DWI. Conclusion The misdiagnosis of pitocytic astrocytomas was most likely caused by atypical features, including calcification ,hemorrhage, CSF dissemination, polynesic lesions and nonspeeific enhancement. The special MRS of pilocytic astrocytomas may also lead to mistaken diagnosis. In children, when the brain tumor was isoto-hypointensity on DWI with clear margin and slight/non peripheral edema, pilocytic astrocytoma should be considered in the differential diagnosis.