Please cite this article in press as: Yaakup NA, et al. Pilomyxoid astrocytoma of the fornix imitating a colloid cyst. Eur J Radiol Extra (2009), doi:10.1016/j.ejrex.2009.05.009 ARTICLE IN PRESS G Model EJREX-796; No. of Pages 4 European Journal of Radiology Extra xxx (2009) xxx–xxx Contents lists available at ScienceDirect European Journal of Radiology Extra journal homepage: intl.elsevierhealth.com/journals/ejrex Pilomyxoid astrocytoma of the fornix imitating a colloid cyst Nur Adura Yaakup a , Kartini Rahmat a,* , Norlisah Mohd Ramli a , N. Vairavan b , Vicknes Waran b , K.T. Wong c a Department of Biomedical Imaging, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia b Department of Neurosurgery, University of Malaya, 50603 Kuala Lumpur, Malaysia c Department of Pathology, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 20 April 2009 Accepted 25 May 2009 Available online xxx Keywords: Pilomyxoid astrocytoma Imaging features Colloid cyst abstract Pilomyxoid astrocytoma is a recently described pediatric brain tumour with distinct histological features and has been shown to behave more aggressively than pilocytic astrocytoma. Pilomyxoid astrocytomas usually involve the hypothalamic/chiasmatic region with imaging features similar to pilocytic astrocy- toma. We report a case of pilomyxoid astrocytoma in the fornix with imaging features imitative of colloid cyst. © 2009 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Pilomyxoid astrocytoma (PMA) is a recently described pediatric brain tumour. PMAs were previously classified within the pilocytic astrocytoma (PA) category. However, PMA has distinct histologi- cal features and has been shown to behave more aggressively than PA. Majority of previously reported PMAs involved the hypotha- lamic/chiasmatic region with similar imaging features of PA. We describe a case of PMA in the fornix with an atypically imaging features imitative of colloid cyst. 2. Case report A 6-year-old girl presented with progressive headache and vom- iting of 1 week with 2 episodes of generalized tonic clonic seizures. She was brought to the Emergency Department in a confused state with Glasgow Coma Scale of 13 (E4M5V4). Magnetic resonance imaging (MRI) of the brain revealed a homogenous, well circum- scribed, oval mass in the anterior aspect of the third ventricle. This mass was isointense on T1-weighted, hyperintense on T2-weighted and FLAIR images. There was no enhancement with intravenous Gd- DTPA. There was acute obstructive hydrocephalus with obstruction of the foramina of Monro bilaterally. The third and fourth ventri- cles were not dilated (Figs. 1 and 2). Computed Tomography (CT) scan showed a slightly hyperdense lesion (Fig. 3). Initial diagno- sis of colloid cyst was made based on the clinical presentation * Corresponding author. Tel.: +60 163114559; fax: +60 379494603. E-mail address: katt xr2000@yahoo.com (K. Rahmat). and imaging findings. The patient underwent a stereotactic endo- scopic procedure with the purpose to decompress and excise the cyst as well as to relieve the hydrocephalus. Intraoperatively, the lesion was found to be solid and lobulated, occupying the anterior part of the third ventricle measuring about 1.5cm × 2.5 cm. Biopsy was performed along with septum pellucidotomy and placement of extra-ventricular drain to relieve the hydrocephalus. Patient subse- quently underwent craniotomy for excision of the tumour, where a gel-like tumour arising from the fornix was excised. A residual rim of tumour was left behind. Histopathological examination of the specimen showed piloid astrocytes disposed in a fibrillary to myxoid background. The tumour cells were uniform with round to oval nuclei and hair-like cytoplasmic processes. There were no Rosenthal fibers, eosinophilic granular bodies, mitosis or endothelial proliferation (Fig. 4). The diagnosis of pilomyxoid astrocytoma WHO Grade 1 was made. Post-operative recovery was complicated by transient diabetes insipidus with hypocortisolism and bilateral subdural collections requiring surgical drainage. There were also neurological compli- cations where the patient developed generalized spasticity and cognitive impairment. Patient was discharged 2 months later. A follow-up MRI was scheduled about 4 months after discharge to assess the residual tumour and plan further management, but unfortunately the patient defaulted follow-up. 3. Discussion Pilomyxoid astrocytoma (PMA) was introduced as a clinico- pathological entity by Tihan et al. in 1999 [1]. Similar to pilocytic astrocytoma (PA), PMA may occur anywhere along the neuraxis and 1571-4675/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrex.2009.05.009