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Showing posts from November 6, 2023
  Hemangioblastoma 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 DIFFERENTIAL DIAGNOSES • Metastasis (most common posterior fossa parenchymal mass in adults) • Pilocytic astrocytoma (most common neoplasm with cyst + nodule in child) • Cavernous malformation • Hereditary hemorrhagic telangiectasia PATHOLOGY • WHO grade I • Red or yellowish, well-circumscribed, unencapsulated, highly vascular mass that abuts leptomeninges • Histology shows stromal cells, innumerable small vessels CLINICAL ISSUES • Headache is most common presenting symptom • Primary therapy = s
  Primary CNS Lymphoma 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: Low relative cerebral blood volume ratios • Periventricular location and subependymal involvement is characteristic of PCNSL • Corpus callosum involvement may be seen with PCNSL, glioblastoma (GBM), and rarely metastases or demyelination TOP DIFFERENTIAL DIAGNOSES • Acquired toxoplasmosis • GBM • Abscess • Progressive multifocal leukoencephalopathy PATHOLOGY • 98% diffuse large B-cell, non-Hodgkin lymphoma CLINICAL ISSUES • Imag
  Germinoma 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 change • Suprasellar germinoma ○ Absent posterior pituitary "bright spot" ○ "Fat" stalk/pituitary gland ○ Strong, relatively uniform enhancement ○ May have cysts, hemorrhage (rare) • Basal ganglia germinoma ○ Rare; hemorrhage common TOP DIFFERENTIAL DIAGNOSES • Pineal germinoma ○ Pineocytoma, other pineal GCTs • Suprasellar germinoma ("fat" infundibulum) ○ Adult = neurosarcoid, metastases ○ Child = Langerhans
  Medulloblastoma 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) ○ Restricted diffusion, low ADC ○ T1 C+ essential to detect CSF dissemination TOP DIFFERENTIAL DIAGNOSES • Atypical teratoid/rhabdoid tumor • Ependymoma • Cerebellar pilocytic astrocytoma PATHOLOGY • WHO grade IV (overstates risk of WNT MB) • Microscopy ○ "Small round blue cell" tumor ○ Neuroblastic (Homer Wright) rosettes (40%) • Most common histologic type = classic MB • Less common subtypes: Desmoplastic, MB with extensive nodularity, large cell/anapla
  Pineocytoma 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 • CT ○ Circumscribed iso-/hypodense pineal region mass ○ Peripheral ("exploded") Ca++ common ○ CECT: Enhances (solid, ring, nodular) • MR (most sensitive) ○ Cystic change may be present ○ Enhancement may be solid or peripheral TOP DIFFERENTIAL DIAGNOSES • Nonneoplastic pineal cyst • PPTID • Pineoblastoma • Germinoma, other germ cell tumors CLINICAL ISSUES • Headache, dorsal midbrain (Parinaud) syndrome most common features • Increased intracranial pressure, ataxia, hydrocephalus, mental status changes may occur • Most common
  Pineal Parenchymal Tumor of Intermediate Differentiation (PPTID) 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 with gray matter, + small hyperintense foci ○ FLAIR: Hyperintense ○ Strong, heterogeneous enhancement ○ MRS: Elevated Cho, decreased NAA • If aggressive-looking pineal region tumor in middle-aged, older adult, consider PPTID TOP DIFFERENTIAL DIAGNOSES • Germinoma • Pineocytoma • Pineoblastoma • Papillary tumor of pineal region PATHOLOGY • Neuroepithelial neoplasm ○ Arises from pineocytes or their precursors • WHO grade
  Central Neurocytoma 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, ↓ N-acetylaspartate; glycine peak at 3.55 ppm • If "bubbly," "feathery," or solid intraventricular mass near foramen of Monro in young adult, consider CN TOP DIFFERENTIAL DIAGNOSES • Subependymoma • Subependymal giant cell astrocytoma • Intraventricular metastasis • Ependymoma • Choroid plexus papilloma CLINICAL ISSUES • Young adults, commonly 20-40 years of age • Usually benign, local recurrence is uncommon ○ Surgical rese
  Ganglioglioma 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 circumscribed • Calcification is common (up to 50%) • Superficial lesions may expand cortex, remodel bone • ~ 50% enhance • Protocol advice: Contrast-enhanced MR to include coronal T2 images for better evaluation of temporal lobes TOP DIFFERENTIAL DIAGNOSES • Pleomorphic xanthoastrocytoma • Dysembryoplastic neuroepithelial tumor • Astrocytoma • Oligodendroglioma • Neurocysticercosis PATHOLOGY • WHO grade I or II (80% grade I) • Uncommon: Anaplastic ganglioglioma (WHO III) • Rare: Mali
  Dysembryoplastic Neuroepithelial Tumor (DNET) 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 20-30% ○ Higher rate of recurrence if enhancement TOP DIFFERENTIAL DIAGNOSES • Focal cortical dysplasia type II (Taylor type) • Neuroepithelial cyst • Ganglioglioma • Pleomorphic xanthoastrocytoma • Angiocentric glioma PATHOLOGY • WHO grade I • Hallmark = specific glioneuronal element CLINICAL ISSUES • Longstanding drug-resistant partial complex seizures in child/young adult • Surgical resection

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