CNS Tumors

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).

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.
• 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).
  • 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:

  Syndrome	Key CNS Tumors	Mnemonic
  NF1	Optic nerve gliomas, astrocytomas, neurofibromas.
  NF2	Bilateral vestibular schwannomas (acoustic neuromas), multiple meningiomas, ependymomas.	📌 MISME: Multiple Inherited Schwannomas, Meningiomas, and Ependymomas
  VHL	Hemangioblastomas (cerebellum, retina, spinal cord), renal cell carcinoma, pheochromocytoma.
  TSC	Subependymal 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.