Pleomorphic xanthoastrocytoma (PXA), first described by Kepes et al. in 1979, is a rare neoplasm that accounts for less than 1% of all astrocytic tumors [1] . It had been considered as a low-grade astrocytic tumor with a relatively favorable prognosis compared to other astrocyte-derived tumors, and is classified as grade II in the World Health Organization (WHO) classification [1] [2] . But this situation must be interpreted with much caution because of some rapid progression or some malignant transformation during the follow-up. Some PXAs can recur, become malignant or fateful for a patient [2] [3] [4] [5] . In this paper, we report a well-documented case of a malignant transformation of a cerebellar PXA with poor prognosis and we discuss the clinical course, surgical management and therapeutic findings on this special case.

This 39 year-old woman, with no medical history, was admitted in our department for headache, vomiting and gait disturbance six months ago. Neurological examination only found a slight cerebellar ataxia with increased deep and superficial reflex. There was no deficit and no papilledema in ophtalmological test. A cranial CT scan showed a cystic midline isodense cerebellar lesion enhanced by contrast injection (Figure 1(a)). She underwent a midline suboccipital craniectomy procedure that allowed to a wholly gross total resection (Figure 1(b)). Histological examination of surgical specimen confirmed a diagnosis of PXA without anaplasia. She was discharged on the tenth postoperative day without any complications. A second postoperative CT scan 8 months later shown no evidence of recurrence (Figure 1(c)).

But, two years after the first surgery, she had been readmitted in emergency with the same clinical symptoms associated with vertigo and intermittent visual

lost. A CT scan revealed a recurrence of the posterior fossa mass, which became bigger than the first one, majority solid and associated to a tetraventricular hydrocephalus (Figure 2(b)). She had had ventriculoperitoneal shunt following a week later by a new posterior fossa approach. During this last operation, we found a grey-yellow median-density tumor with cystic cavities in posterior cranial fossa. We had some difficulties in differentiating the tumor from the normal cerebellar structures, so subtotal resection was performed. This time, histopathology examination demonstrated “a PXA with rapid progression or malignant transformation, astrocytoma WHO grade III” (Figure 2(b)). So, the patient was discharged with the advice for further radiotherapy. But two months later, she was received in severe cachexia and high nuchal rigidity. No radiotherapy had been done in our case. CT scan showed a recurrence of the mass that is large in size from all the posterior fossa to the supratentorial area. Due to the rapid progression of the tumor and the lack of therapeutic treatment options available to us, we decided to stop treatment after discussions with her family. She died three days later (Figure 2(c)).

PXA is a low-grade astrocytoma that corresponds to a WHO grade II [6] . The majority of PXA cases occur in a supratentorial location within the temporal followed by parietal, frontal and occipital lobes [7] [8] . However, pure cerebellar PXA are very rare. Only 16 cases of cerebellar PXA had been related in the literature from which three had a malignant transformation (Table 1). The time from diagnosis to malignancy features was approximately 24 months in our case. Cerebellar PXA was more prevalent in females. Two-thirds of cerebellar PXAs occurred in adults and the average age at the time of diagnosis was 33 years. In contrast, supratentorial forms were observed in patients with a younger average age (21 - 26 years) [3] [4] . The main clinical signs in our case were headache, vomiting, and gait disturbance.