Composite pleomorphic xanthoastrocytoma-ganglioglioma. Report of a case

Pleomorphic xanthoastrocytoma (PXA) constitute a rare variant of low-grade astrocytoma, usually supratentorial that generally occurs in the second to fourth decade of life. The typical clinical presentation usually involves seizures. Surgery is the mainstay treatment with excellent prognosis. Ganglioglioma (GG) represents approximately 1.3% of brain tumors and complete resection is generally curative. Composite pleomorphic xanthoastrocytoma-ganglioglioma (PXA-GG) is a rare recently recognized entity. Only 16 cases have been documented so far in the literature. PXA-GG usually occurs in patients younger than 30 years of age and has a predilection for the temporal lobe. Nevertheless, cerebellum is frequently affected. PXA-GG usually presents with seizures or headache and on the radiological work-up [computed tomography (CT) and magnetic resonance imaging (MRI)] in the majority of cases it has a solid and cystic component. Herewith, we report a case of a 3-year-old boy who presented with an 1-week history of headache and seizures. The patient was initially evaluated in another hospital by CT that revealed a lesion in the right parietal-occipital lobe measuring approximately 13x10.2mm, without edema and mass effect. After contrast administration there was marked enhancement. Differential diagnosis included the presence of a tumor and a vascular malformation. The patient was referred for further evaluation in our institute. A MRI study was performed and revealed a solid mass with low signal intensity on T1 and T2-weighted images that homogenously enhanced after gadolinium administration. A digital subtraction angiography was also performed and excluded the presence of a vascular malformation. The patient was operated upon via a parietal-occipital craniotomy. The tumor was totally resected. Postoperative the patient was neurological intact. Histology revealed the presence of an anaplastic PXA-GG (WHO grade II), which is composed of two distinct tissue elements that of the PXA and GG. Immunochemistry revealed that the spindled cells were positive for glial fibrillary acidic protein (GFAP) whereas the cells with gaglionic features were positive for synaptophysin, neurofilaments and chromogranin A. There were few mitotic figures (2-12 mitosis/10hpf x 40). The Ki-67/MIB-1 index was 5-10%. The p53 protein was detected in 10-15% of the nucle. Additional the bcl-2 protein was detected in 15-20% of the tumor cells and the epidermal growth factor receptor (EGFR) in >20%. Due to tumor's anaplastic features the patient was referred in the oncology department for further treatment. On follow up radiological evaluation (MRI) after one year, no tumor recurrence was noted.

Our case is very unusual since this presentation is the youngest case and a tumor located in the parietal-occipital lobe has not been reported so far. Furthermore, the Ki-67/MIB-1 index has been reported to be 1.7-5.7% whereas in our case was 5-10%. The p53 index has been rarely reported in the literature and so far its prognostic role has not been totally clarified. Moreover, the high mitotic index has not been associated with worsen prognosis but only with higher incidence of tumor recurrence. The exact prognosis of PXA-GG is difficult to estimate since this tumor is extremely rare. Nevertheless, the clinical behavior of PXA-GG has been reported usually benign after complete surgical excision. For that reason gross total resection should be the goal. Additionally, there were two reports of postoperative radiotherapy with good results. However, there is no adequate experience regarding the value of postoperative radiotherapy, mainly in cases where a complete tumor excision has been accomplished and also in children where the side-effects of irradiation may be disastrous. There is usually no tumor recurrence; nevertheless, there is one report of a PXA-GG that dedifferentiated after 17 years to glioblastoma multiforma. To conclude, PXA-GG constitutes an uncommon tumor with usually good long term outcome. Nonetheless, close follow-up is mandatory, because PXA-GG may exhibit malignant degeneration. Encephalos 2009, 46(1):40-43.

Key words: Pleomorphic xanthoastrocytoma, ganglioglioma, children.