CNS Tumors

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CNS Tumors Intro & Astrocytomas - Brainy Beginnings & Star Cells

  • WHO Classification: Grades I (benign) to IV (malignant).
  • Clinical: ↑ ICP (headache, vomiting, papilledema), focal deficits.
  • Astrocytomas (GFAP+):
    • Pilocytic Astrocytoma (WHO Grade I):
      • Children, cerebellum.
      • Rosenthal fibers, Eosinophilic Granular Bodies (EGBs). BRAF alterations.

      ⭐ Rosenthal fibers (corkscrew eosinophilic inclusions) are classic in Pilocytic Astrocytoma.

    • Diffuse Astrocytoma (WHO Grade II):
      • IDH-mutant (better prognosis) vs. IDH-wildtype.
    • Anaplastic Astrocytoma (WHO Grade III):
      • Higher grade; IDH-mutant vs. IDH-wildtype.
  • Glioblastoma (GBM, WHO Grade IV):
    • Most common primary malignant. GFAP+.
    • IDH-wildtype (primary, older) vs. IDH-mutant (secondary, younger, from lower-grade).
    • Histology: Pseudopalisading necrosis, microvascular proliferation.
    • "Butterfly glioma" (crosses corpus callosum).
    • MGMT promoter methylation: ↑ temozolomide response.
    • 📌 GBM: Grim Butterfly Malignancy (GFAP+, Butterfly, Microvascular/Necrosis). Glioblastoma histology features

Oligo, Ependymal & Neuronal Tumors - Code Breakers & Neuron Nurturers

  • Oligodendroglioma:
    • Key: 1p/19q codeletion (favorable prognosis, chemo-predictive), IDH-mutant.
    • Micro: 'Fried egg' cells (uniform, clear cytoplasm), 'chicken-wire' vasculature, calcification. Oligodendroglioma histology: fried egg cells, chicken wire
  • Ependymoma:
    • Location: Children (4th ventricle); adults (spinal cord, common intramedullary).
    • Histo: Perivascular pseudorosettes (key), true ependymal rosettes (around lumen).
    • Subtypes: Myxopapillary (cauda equina/filum terminale), Subependymoma (ventricular, incidental).
  • Choroid Plexus Tumors:
    • Papilloma (CPP): Benign, children, causes hydrocephalus (↑ CSF production).
    • Carcinoma (CPC): Malignant, rare, aggressive, mainly children.
  • Neuronal & Mixed Tumors:
    • Ganglioglioma: Children, temporal lobe; cystic with mural nodule; chronic seizures.
    • DNET (Dysembryoplastic Neuroepithelial Tumor): Children/young adults; cortical; drug-resistant seizures; 'floating neurons' in mucinous pools.

1p/19q co-deletion in Oligodendroglioma is a key marker indicating favorable prognosis and predicts better chemotherapy response.

Embryonal, Meningeal & Metastatic Tumors - Tiny Terrors, Dural Dwellers & Unwanted Guests

  • Embryonal: Medulloblastoma
    • Children, cerebellum (vermis/4th ventricle roof). Highly malignant, radiosensitive; CSF dissemination.
    • Histology: Small round blue cells, Homer Wright rosettes (neuroblastic). Medulloblastoma with Homer Wright rosettes
    • Molecular: WNT (best prognosis); SHH; Group 3 (MYC, worst); Group 4 (commonest).

    ⭐ Homer Wright rosettes are characteristic of Medulloblastoma.

  • Meningioma
    • Arachnoid cap cells. Usually benign (Grade I), slow-growing. Dural attachment ("dural tail").
    • Common sites: Parasagittal, falx, sphenoid wing. ↑ Adult females (estrogen receptors).
    • Histology types: Syncytial, fibroblastic, transitional. Psammoma bodies (calcified whorls). WHO Grades I-III.
  • Metastatic Tumors
    • Most common intracranial tumors in adults (vs. primary).
    • Common primaries: 📌 LBM-RC (Lung, Breast, Melanoma, Renal, Colorectal).
    • Multiple, well-circumscribed lesions at grey-white junction or watershed areas. Ring enhancement, vasogenic edema.

Molecular Markers & Syndromes - Code Red & Family Ties

  • Molecular Markers:
    • IDH1/2 mutations (gliomas - better prognosis).
    • 1p/19q codeletion (oligodendrogliomas - chemosensitive).
    • MGMT promoter methylation (GBM - predicts temozolomide response).
    • TP53, ATRX, TERT promoter mutations.
    • EGFR amplification (GBM).
    • BRAF V600E (Pilocytic astrocytoma, Ganglioglioma).
  • Neurocutaneous Syndromes & CNS Tumors:
    SyndromeKey CNS TumorsMnemonic
    NF1Optic nerve gliomas, astrocytomas, neurofibromas.
    NF2Bilateral vestibular schwannomas (acoustic neuromas), multiple meningiomas, ependymomas.📌 MISME: Multiple Inherited Schwannomas, Meningiomas, and Ependymomas
    VHLHemangioblastomas (cerebellum, retina, spinal cord), renal cell carcinoma, pheochromocytoma.
    TSCSubependymal giant cell astrocytomas (SEGA), cortical tubers, subependymal nodules.📌 HAMARTOMAS

⭐ Bilateral vestibular schwannomas are pathognomonic for NF2.

High‑Yield Points - ⚡ Biggest Takeaways

  • Glioblastoma: Most common adult primary; GFAP +ve; pseudopalisading necrosis; butterfly glioma.
  • Pilocytic Astrocytoma: Most common childhood primary; Rosenthal fibers; GFAP +ve; biphasic pattern.
  • Meningioma: Psammoma bodies; from arachnoid cap cells; dural tail sign; often benign.
  • Medulloblastoma: Homer Wright rosettes; malignant childhood tumor (cerebellum); drop metastases.
  • Oligodendroglioma: "Fried egg" cells; chicken-wire capillaries; often calcified; 1p/19q co-deletion.
  • Ependymoma: Perivascular pseudorosettes; typically 4th ventricle (children); GFAP +ve.
  • Craniopharyngioma: From Rathke's pouch; suprasellar calcification; "motor oil" fluid; bitemporal hemianopsia.

Practice Questions: CNS Tumors

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Meningioma is a _____ tumor of arachnoid cells

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Meningioma is a _____ tumor of arachnoid cells

benign

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