ABSTRACT
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 T1 WI and 7 had hyperintensity on T2 WI. 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 PMAon CT and MRimages,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.
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Objective To compare the difference of MRI characteristics of pilomyxoid astrocytomas (PMA)and pilocytic astrocy-tomas (PA)in hypothalamus/optic chiasma region.Methods The MR images and clinical materials of 20 PMAs and 20 PAs proved by pathology were reviewed retrospectively.Imaging characteristics and clinical materials were analyzed,including age,gender, size,the signal characteristics of the tumor,growth,enhancement pattern,hydrocephalus and leptomeningeal dissemination.Results There were statistically significant differences in streaky low signal intensity among the high intensity of T2 WI and leptomeningeal dissemination between PMA and PA (P <0.05).However,no statistically significant differences were found in the other character-istics and clinical materials between the two types of tumors.Conclusion PMA and PA in hypothalamus/optic chiasma region are difficult to make differential diagnosis.The streaky low signal intensity among the high intensity of T2 WI and more frequent lepto-meningeal dissemination are helpful differential features of PMA as compared to PA.
ABSTRACT
Pilomyxoid astrocytoma (PMA) is a recently described brain tumor. PMA shares similar features with pilocytic astrocytoma (PA), the most common central nervous system (CNS) tumor in the pediatric population, yet displays subtle histologic differences. We describe a case of PMA in a six-year-old male involving sellar and suprasellar region presenting with failure to thrive and delayed developmental milestones. The histological findings revealed a tumor composed of a monotonous population of loosely arranged cells with delicate piloid like processes, within a prominent myxoid background. The tumor lacked biphasic appearance, Rosenthal fibers, eosinophilic granular bodies and calcification that are commonly observed in classical PA. Previous studies have shown PMA to behave more aggressively than PA, with shorter progression-free survival as well as a higher rate of recurrence and CNS dissemination. Thus, recognition of PMA and its distinction from classical PA is very important.
ABSTRACT
Pilomyxoid astrocytoma (PMA) is a newly recognized variant of a pilocytic astrocytoma. This report describes a case of a pilomyxoid astrocytoma that occurred in the opticohypothalamus. The patient was a 18-year-old girl who complained decreased visual acuity and visual field over a period of two years. Magnetic resonance imaging (MRI) showed an irregular lobulated tumor with heterogeneous enhancement at the suprasellar region involving the hypothalamus. The mass was partially removed via the subfrontal approach. Its pathology was confirmed to be PMA. Adjuvant chemotherapy with cisplatin and vincristine was started following tumor resection. After four cycles, the mass showed a partial response to the chemotherapy. Although long-term outcome is yet to be determined, the administration of combined cisplatin and vincristine treatment seems to be an effective regimen for a pilomyxoid astrocytoma.