KEY FACTS Terminology Malignant primary CNS neoplasm primarily composed of B lymphocytes (PCNSL) Imaging Best diagnostic clue: Enhancing lesion(s) within basal ganglia &/or periventricular white matter 60-80% supratentorial Often involve, cross corpus callosum Frequently contact, extend along ependymal surfaces Classically hyperdense on CT (helpful for diagnosis) Diffusely enhancing periventricular mass in immunocompetent patients May see hemorrhage or necrosis in immunocompromised patients DWI: Low ADC values PWI:…

KEY FACTS Terminology Hemangioblastoma (HGBL): Highly vascular tumor of adults most commonly found in posterior fossa (PF), spinal cord 25-40% of HGBLs in von Hippel-Lindau disease (VHL) Imaging Best diagnostic clue: Adult with cerebellar mass with cyst and enhancing mural nodule General features 50-60% cyst + “mural” nodule; 40% solid enhancing mass 90-95% in posterior fossa 5-10% supratentorial (around optic pathways, hemispheres; usually in VHL) Top…

KEY FACTS Terminology Medulloblastoma (MB) Malignant, invasive, highly cellular embryonal tumor 4 distinct MB molecular subgroups Wingless (WNT) Sonic hedgehog (SHH) Group 3 Group 4 Imaging MB subgroups arise in different locations Midline (4th ventricle) – Predominately (but not exclusively) groups 3 and 4 Cerebellar peduncle/CPA cistern: WNT Cerebellar hemispheres (lateral): SHH NECT: 90% hyperdense (Ca++, hemorrhage uncommon) MR: > 90% enhance (group 4 minimal/no enhancement)…

KEY FACTS Terminology Intracranial germ cell tumor (iGCT) iGCTs are intracranial homologue of gonadal germinomas (ovarian dysgerminoma, testicular seminoma) Imaging Most common: In/near midline (80-90%) Pineal region ~ 50-65% Suprasellar ~ 25-35% Less common: Basal ganglia/thalami ~ 5-10% 20% multiple Most common = pineal with suprasellar Pineal germinoma Hyperdense pineal region mass engulfs pineal Ca++ Strong, often heterogeneous enhancement T2/FLAIR hyperintensity in surrounding brain = inflammation/granulomatous…

KEY FACTS Terminology Primary parenchymal neoplasm of pineal gland Intermediate in malignancy between pineoblastoma and pineocytoma Imaging General features Aggressive-looking pineal mass in adult Extension into adjacent structures (ventricles, thalami) is common Lobulated, moderately vascular Size varies from small (< 1 cm) to large (~ 6 cm) CT Hyperdense mass centered in pineal region Engulfs pineal gland Ca++ Hydrocephalus MR T1: Mixed iso-/hypointense mass T2: Isointense…

KEY FACTS Terminology Pineocytoma (PC), pineal parenchymal tumor (PPT) PCs are composed of small, uniform, mature cells Cells resemble pineocytes Imaging General features: Circumscribed, enhancing pineal mass May mimic benign pineal cyst or PPT of intermediate differentiation (PPTID) Typically < 3 cm May compress adjacent structures Rarely extends into 3rd ventricle, rarely invasive Can compress aqueduct → hydrocephalus Occasionally hemorrhages CT Circumscribed iso-/hypodense pineal region mass…

KEY FACTS Terminology Central neurocytoma (CN) = intraventricular neuroepithelial tumor with neuronal differentiation Imaging Best diagnostic clue: “Bubbly” mass in frontal horn or body of lateral ventricle May involve 3rd ventricle CT: Usually mixed solid and cystic mass with calcification Hydrocephalus common Rarely complicated by hemorrhage MR: Heterogeneous, T2 hyperintense, “bubbly” appearance May be predominantly solid mass Moderate to strong heterogeneous enhancement MRS: ↑ Cho, ↓…

KEY FACTS Terminology Dysembryoplastic neuroepithelial tumor (DNET) Benign mixed glial-neuronal neoplasm Frequently associated with cortical dysplasia Imaging May occur in any region of supratentorial cortex Temporal lobe most common, followed by frontal lobe Mass frequently “points” toward ventricle Sharply demarcated, wedge-shaped Cystic (“bubbly”) intracortical mass Minimal/no mass effect No surrounding edema Slow growth over years Usually does not enhance Faint focal punctate or ring enhancement in…

KEY FACTS Terminology Well-differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells Most common neoplastic cause of temporal lobe epilepsy (TLE) Imaging Best diagnostic clue: Partially cystic, enhancing, cortically based mass in child/young adult with TLE Can occur anywhere, but most commonly superficial hemispheres, temporal lobe (> 75%) Circumscribed cyst with mural nodule most common May be solid and appear well…

KEY FACTS Terminology Choroid plexus tumor (CPT) 3 types of CPTs – Choroid plexus papilloma (CPP) (WHO grade I) – Atypical CPP (aCPP) (grade II) – Choroid plexus carcinoma (CPCa) (grade III) Imaging Classic: Child with enhancing lobulated (cauliflower-like) mass in atrium of lateral ventricle CPPs occur in proportion to amount of choroid plexus 50% in lateral ventricle (usually atrium) 40% in 4th ventricle &/or foramina…

KEY FACTS Terminology Rare, benign, well-differentiated, intraventricular ependymal tumor, typically attached to ventricular wall Imaging Intraventricular, inferior 4th ventricle typical (60%) Other locations: Lateral > 3rd ventricle > spinal cord T2/FLAIR hyperintense intraventricular mass Heterogeneity related to cystic changes; blood products or Ca++ may be seen in larger lesions Variable enhancement, typically none to mild T2WI and FLAIR are often most sensitive sequences Top Differential Diagnoses…

KEY FACTS Terminology Posterior fossa ependymoma (PF-EPN) Imaging Ependymoma can occur anywhere in neuraxis Most common site: Posterior fossa (2/3 of cases) Lobulated mass in body/inferior 4th ventricle – Soft or “plastic” tumor □ Accommodates to shape of ventricle □ Squeezes through foramen of Magendie into cisterna magna □ ± extension through foramina of Luschka into cerebellopontine angle cisterns NECT Ca++ common (50%) ± cysts, hemorrhage…

KEY FACTS Terminology Oligodendroglioma with focal or diffuse histologic features of malignancy Imaging Best diagnostic clue: Calcified frontal lobe mass involving cortex and subcortical white matter Frontal lobe is most common location, followed by temporal lobe Majority have nodular or clumped calcification May see hemorrhage or necrosis Variable enhancement Anaplastic oligodendroglioma more likely to enhance than low-grade oligo Neoplastic cells almost always found beyond areas of…

KEY FACTS Terminology Well-differentiated, slowly growing but diffusely infiltrating cortical/subcortical tumor Imaging Most common site is frontal lobe (50-65%) Best diagnostic clue: Partially calcified subcortical/cortical frontal mass in middle-aged adult Typically T2 heterogeneous, hyperintense mass ~ 50% enhance Heterogeneous enhancement is typical New enhancement in previously nonenhancing oligodendroglioma suggests malignant progression Top Differential Diagnoses Anaplastic oligodendroglioma Low-grade diffuse astrocytoma Ganglioglioma Dysembryoplastic neuroepithelial tumor Pleomorphic xanthoastrocytoma Cerebritis…

KEY FACTS Terminology Diffusely infiltrating, frequently bilateral glial tumor involving at least 3 lobes Infiltrative extent of tumor is out of proportion to histologic and clinical features Imaging T2 hyperintense infiltrating mass with enlargement of involved structures Typical cerebral hemispheres (75%) Brain architecture enlarged, distorted, but preserved Typically no or minimal enhancement Enhancement may indicate malignant progression or focus of malignant glioma MRS: Increased choline, decreased…

KEY FACTS Terminology Rapidly enlarging malignant astrocytic tumor characterized by necrosis and neovascularity Most common of all primary intracranial neoplasms Imaging Best imaging clue: Thick, irregularly enhancing rind of neoplastic tissue surrounding necrotic core Heterogeneous, hyperintense mass with adjacent tumor infiltration/vasogenic edema Necrosis, cysts, hemorrhage, fluid/debris levels, flow voids (neovascularity) may be seen Supratentorial white matter most common location Cerebral hemispheres > brainstem > cerebellum Viable…

KEY FACTS Terminology Pilocytic astrocytoma (PA): Well-circumscribed, slow-growing tumor, often with cyst and mural nodule Imaging Cystic cerebellar mass with enhancing mural nodule Arises from cerebellar hemisphere and compresses 4th ventricle Enlarged optic nerve/chiasm/tract with variable enhancement Cerebellum (60%) > optic nerve/chiasm (25-30%) > adjacent to 3rd ventricle > brainstem Well circumscribed with little to no edema Aggressive appearance (enhancement and MRS) of tumor is misleading…

KEY FACTS Terminology Diffusely infiltrating malignant astrocytoma with anaplasia, marked proliferative potential Imaging Infiltrating mass that predominately involves white matter with variable enhancement T2 heterogeneously hyperintense Neoplastic cells almost always found beyond areas of abnormal signal intensity May involve and expand overlying cortex Usually no enhancement; focal, nodular, homogeneous, patchy enhancement less common Ring enhancement is suspicious for glioblastoma (GBM) MRS: Increased Cho/Cr ratio, decreased N…

KEY FACTS Terminology Well-differentiated but infiltrating neoplasm, slow growth pattern Primary brain tumor of astrocytic origin with intrinsic tendency for malignant progression, degeneration into anaplastic astrocytoma (AA) Imaging Focal or diffuse nonenhancing white matter mass T2 homogeneously hyperintense mass May expand adjacent cortex Usually no enhancement Enhancement suggests progression to higher grade MRS: High choline, low NAA typical but not specific Perfusion: Relatively lower rCBV compared…

Introduction The most widely accepted classification of brain neoplasms is sponsored by the World Health Organization (WHO). A working group of world-renowned neuropathologists periodically convenes for a consensus conference on brain tumor classification and grading. The results are then published. An update to the 2007 edition of the so-called “Blue Book” is scheduled for early 2017. Brain tumors are both classified and graded. Although this is…