Abstract
Background:Glioblastoma with oligodendroglioma component (GBMO) is a recently classified subtype of glioblastoma, which carries different clinical and prognostic outcomes, being frequently misdiagnosed. Both glioblastoma and GBMO are mainly seen in older ages, such as the 5th and 6th decades of life, being an extremely rare occurrence in children or adolescents and more frequent in male patients. 
 Case report: A 15-year-old girl, presented with history of daily headache, not relieved by painkillers, vomiting, blurred vision and strabismus. Magnetic resonance imaging of the brain revealed expansive tumour on left temporo-occipital lobe. Patient was submitted to intracranial exeresis, along with histopathological examination: glial neoplasm with areas of pleomorphism, hyperchromatism, anaplasia, foci of oligodendroglial component, perinuclear halo and ramified capillaries, resembling oligodendroglioma, necrosis and intense mitotic activity. The immunohistochemical analysis revealed positive Glial Fibrillary Acidic Protein (GFAP), synaptophysin, Ki-67 (MindBomb E3 ubiquitin protein ligase 1 – MIB-1)and hyperexpression of Epidermal Growth Factor Receptor (EGFR), indicating GBMO. Subsequently, Fluorescence in situ Hybridization (FISH) showed 1p/19q codeletion and Isocitrate Dehydrogenase 1 (IDH 1) mutation, suggesting an oligodendroglioma component. Tumour resection was total and symptoms disappeared. Afterwards, she started adjuvant oral chemotherapy with temozolomide. Treatment was completed nine months after the diagnosis, with no greater symptoms or complications and complete remission. 
 Conclusion: GBMO must be considered as a possible diagnosis when confronted with a malignant glioma with oligodendroglial tumour component, independent of age or genre. Necrosis upon histopathological examination has a strong relation to shorter median overall survival. IDH mutation and 1p/19q codeletion should be analyzed by immunohistochemistry. Total tumour resection, with adjuvant treatment (chemotherapy with temozolomide and radiotherapy), increases benefits and improves prognosis.
Highlights
Glioblastoma with oligodendroglioma component (GBMO) is a recently classified subtype of glioblastoma (GBM), defined in 2007 by World Health Organization (WHO) as a high grade malignant glioma with oligodendroglial tumour component, which carries different clinical and prognostic outcomes [1].according to the most recent WHO classification, in 2016, a new addition was made to this diagnosis: the evidence of isocitrate dehydrogenase (IDH) mutation, which is present on about 10% of gliobastomas [2]
GBMO must be considered as a possible diagnosis when confronted with a malignant glioma with oligodendroglial tumour component, independent of age or genre
GBMO has been said to have a younger onset than GBM, both are mainly seen on older ages, such as the 5th and 6th decades of life, being an extremely rare occurrence on children or adolescents [3, 5, 6]
Summary
GBMO must be considered as a possible diagnosis when confronted with a malignant glioma with oligodendroglial tumour component, even in females, children and adolescents. The presence of necrosis upon histopathological examination of the tumour has a strong relation to shorter median overall survival, being its analysis advised. IDH mutation and 19q deletion should be analyzed by immunohistochemistry, as both are related to longer survival rate and better prognosis, and can be considered for the classification of the tumour. The primary treatment for GBMO is total tumour resection, with adjuvant treatment composed by chemotherapy with temozolomide and radiotherapy, which increases benefits and improves prognosis
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