Pilomyxoid astrocytoma in cerebellum

Pediatric Cerebellar Pilomyxoid Astrocytoma: Clinical and Radiological Findings in Three Cases

Pilomyxoid astrocytomas (PMA) is a particular form of glial tumors distinct from pilocytic astrocytomas (PA). On the last 2016 WHO classification for CNS tumours, no definite grade assignment was proposed for these lesions. They may be more aggressive with a different clinical course compared to PA due to their greater propensity for local recurrence and cerebrospinal dissemination. Most cases arise from the hypothalamic region. Only few studies reported cerebellar localization of the lesion. We report 3 pediatric cases treated for pediatric PMA of the posterior fossa. Clinical, radiological, and prognostic features were reviewed. The age of our patients was between 1 and 9 years old. Signs of intracranial hypertension were found in all patients. One of them presented an increased head circumference and the 2 others had a cerebellar syndrome. Brain CT-scan and MRI displayed a large wellcircumscribed intra-axial solid and cystic posterior fossa tumor. Total surgical resection was performed for all tumors. After a 2 years follow up, no signs of recurrence were noticed. In the literature, PMA been reported with overwhelming majority in children aged between 2 months and 4 years. Despite of many pathological similarities with PAs, PMAs have some specific features in histology, leading to their identification as independent type of glioma. Radiological differential diagnosis between PMAs and Pas can be made using arterial spin labeling imaging, which shows low perfusion parameters in PAs. Clinical and radiological follow up are mandatory do to different natural history and higher rates of local recurrence of this tumor compared to PA. Prognosis is favorable when complete surgical exeresis is possible.

Pilomyxoid astrocytoma in the adult cerebellum

Pilomyxoid astrocytoma (PMA) is a recently recognised World Health Organization (WHO) Grade II tumour that was previously characterised as a subtype of the WHO Grade I pilocytic astrocytoma (PA). PMA has a histological appearance distinct from PA and a poorer prognosis due to its greater propensity for local recurrence and cerebrospinal dissemination. Although originally considered a paediatric tumour involving mainly the hypothalamic and chiasmatic region, reports of the lesion occurring in the adult population and other areas of the neuroaxis are emerging. We review the literature on PMA within the adult population and present the first case of PMA in the cerebellum of an adult female.

A rare case of multicystic disseminated astrocytoma with pilomyxoid characteristics in a 4-year-old child

Pilomyxoid astrocytomas are a more aggressive variant of pilocytic astrocytoma. Over the last 14 years, there has been increasing evidence to suggest that these tumours are distinct pathological entities to pilocytic astrocytomas. Radiological features of these tumours are slowly emerging in the neuroradiological literature. We report a unique radiological appearance of a multicystic, disseminated astrocytoma with pilomyxoid characteristics presenting in a 4-year-old boy and highlight the importance of considering this diagnosis with similar imaging.