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Chapter 10. Neuro-oncology

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What molecular mutation is a predictor of improved overall survival in glioblastoma (World Health Organization [WHO] grade IV astrocytoma)?

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A. PTEN mutation

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B. EGFR mutation

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C. IDH mutation

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D. Ki-67

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E. 1p/19q codeletion

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C. Isocitrate dehydrogenase (IDH) gene mutation is thought to occur as one of the early steps in gliomagenesis and is typically present in both lineages of glial tumors—astrocytomas and oligodendrogliomas. It is postulated that WHO grade IV astrocytomas (glioblastoma) expressing IDH mutation have arisen from a low-grade glioma. The disease course tends to be more favorable than IDH wild-type glioblastomas. P53 mutation is seen in most low-grade astrocytomas but is not a prognostic marker. 1p/19q codeletion is commonly seen in oligodendrogliomas, but not astrocytomas. Ki-67 is a mitosis marker also unrelated to outcome. EGFR and PTEN mutations tend to occur more frequently in primary glioblastomas versus secondary glioblastomas.

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What is the most common primary malignant brain tumor of childhood?

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A. Glioblastoma

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B. Pilocytic astrocytoma

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C. Meningioma (WHO grade I)

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D. Ganglioglioma

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E. Medulloblastoma

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E. Primary brain tumors are the most common solid tumors affecting children under age 10. Medulloblastomas are the most common primary malignant brain tumor of childhood, accounting for 15% to 20% of them. All medulloblastomas are considered high-grade tumors, and they are always located in the infratentorial region and are commonly midline. Medulloblastomas can be stratified into average-risk and high-risk subgroups based on age, disease dissemination, and extent of residual disease after surgical resection. More recently, molecular characterization has also stratified medulloblastomas into 4 groups with different biologic behavior and outcomes. The 5-year overall survival rate is 70% for standard-risk patients who undergo surgical resection, radiotherapy, and chemotherapy. Pilocytic astrocytomas, gangliogliomas, and meningiomas are not malignant brain tumors. Glioblastoma is the most common primary malignant brain tumor in adults.

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A 55-year-old woman with no past medical history presents to the emergency department (ED) with progressive headaches for 2 months prior to presentation. Her neurologic exam is otherwise unremarkable. Brain magnetic resonance imaging (MRI) with contrast reveals an irregularly enhancing 4-cm infiltrating lesion with central necrosis on the right parietal lobe with surrounding vasogenic edema (see figure below). Computed tomography (CT) of the chest, abdomen, and pelvis is unremarkable. Also, blood cultures and transthoracic echocardiography (TTE) were obtained at admission and are also unremarkable. Based on the most likely diagnosis, what is the ...

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