Brain tumors

1. Astrocytoma, IDH-mutant

Age: 4th–6th decades

Location: Cerebral hemispheres

Mutation: IDH1 > IDH2

Grade: WHO 2–4

Presentation: Seizures, headache, focal neurological deficits

Morphology: Poorly defined/infiltrative; ↑ glial nuclei, pleomorphism, fibrillary background

Prognosis: Depends mainly on grade

⭐ Exam: Adult + infiltrative cerebral tumor + IDH mutation

2. Glioblastoma, IDH-wild-type

Age: 6th–8th decades

Location: Cerebral hemispheres

Mutation: IDH-wild-type

Grade: ⭐ WHO 4

Presentation: Rapid progression, seizures, neurocognitive impairment

Gross: ⭐ Necrotic, hemorrhagic, infiltrating mass

Microscopy: Pleomorphic cells + nuclear atypia + brisk mitoses

⭐ Pseudopalisading necrosis

⭐ Microvascular proliferation

Prognosis: ⭐ Very poor

Median survival: ~15–18 months

⭐ Exam: Elderly + rapid progression + necrosis/pseudopalisading = GBM

3. Oligodendroglioma

Age: 4th–5th decades

Location: Cerebral hemispheres

Mutation: ⭐ IDH1/2 + 1p/19q codeletion

Grade: WHO 2–3

Presentation: Long history of symptoms, especially seizures

Microscopy: Sheets of regular cells

⭐ “Fried-egg” appearance

⭐ “Chicken-wire” capillaries

Prognosis: ⭐ Best prognosis among diffuse gliomas

⭐ Exam: IDH + 1p/19q = Oligodendroglioma

4. Pilocytic Astrocytoma

Age: Children & young adults

Location: ⭐ Cerebellum

Mutation: ⭐ BRAF activation mutation/translocation

Behavior: Relatively benign, circumscribed

Presentation: Mass effect, obstructive hydrocephalus, ↑ICP

Gross: ⭐ Cyst + mural nodule

Microscopy: Bipolar cells with long hair-like processes

⭐ Rosenthal fibers

⭐ Eosinophilic granular bodies

Prognosis: Generally favorable

⭐ Exam: Child + cerebellum + cyst/mural nodule = Pilocytic astrocytoma

5. Ependymoma

Age:

Children → first 2 decades

Adults → usually spinal cord

Location:

Children → ⭐ 4th ventricle

Adults → ⭐ spinal cord

Molecular: ZFTA fusion, YAP1 fusion, MYCN amplification

Grade: WHO 2–3

Microscopy: ⭐ True rosettes

⭐ Perivascular pseudorosettes

Tumor processes radiate toward a blood vessel

Prognosis: Supratentorial/spinal tumors do better after complete resection than posterior fossa tumors

⭐ Exam: Child + 4th ventricle + pseudorosettes = Ependymoma

6. Ganglioglioma

Age: Usually young; commonly 1st–2nd decades

Location: ⭐ Temporal lobe

Mutation: BRAF point mutation in ~20–50%

Grade: WHO 1

Presentation: ⭐ Seizures

Morphology: Neoplastic ganglion cells + glial cells

Behavior: Slow-growing

⭐ Exam: Young + temporal lobe + seizures = Ganglioglioma

7. Medulloblastoma

Age: ⭐ Children

Location: ⭐ Cerebellum, often superior vermis

Type: Embryonal/primitive tumor

Behavior: ⭐ Highly malignant

Molecular:

WNT activation → excellent prognosis

SHH + mutant TP53 → very poor prognosis

Gross: Well-circumscribed, gray, friable

Microscopy: ⭐ Small blue primitive cells

⭐ Rosettes around central neuropil

Treatment: ⭐ Highly radiosensitive

Prognosis: With treatment, 5-year survival may reach ~75%

⭐ Exam: Child + cerebellum + small blue cells = Medulloblastoma

8. Meningioma

Age: ⭐ Adults

Origin: Arachnoid meningothelial cells

Location: Usually attached to dura

Association: ⭐ Multiple meningiomas → consider NF2

Grades: WHO 1–3

Gross: Usually well-defined, attached to dura, compresses brain

Microscopy: ⭐ Meningothelial whorls

⭐ Uniform round nuclei

⭐ Intranuclear pseudoinclusions

⭐ ± Psammoma bodies

Prognosis: Depends on size, location, surgical accessibility & grade

Grade 2: ↑ mitoses, brain invasion, necrosis → ↑ recurrence

Grade 3: Rare, highly aggressive

⭐ Exam: Adult + dural-based tumor + whorls = Meningioma