Primary Brain Tumors

Overview

• Presentation
  • Most common complaints are due to mass effects
    • e.g., seizures, dementia, focal lesions, headache
  • majority of adult primary tumors are supratentorial
  • majority of childhood primary tumors are infratentorial
• Primary tumor characteristics
  • rarely undergo metastasis
  • usually poorly circumscribed
  • primary brain tumor frequency
    • meningioma > pituitary tumor > glioblastoma > nerve sheath tumor
  • risk factors
    • NF, cigarette smoking, Turcot’s syndrome (colonic polyps and brain tumor)
• Secondary tumor characteristics
  • 50% of adult brain tumors are due to metastases
  • well circumscribed
  • usually present at gray-white junction 
  • frequency of primary tumor causes
• lung > breast > melanoma (skin) > kidney > GI

Adult peak-incidence tumors

• Glioblastoma multiforme
  • type: grade IV astrocytoma
  • prognosis: grave (< 1 year life expectancy)
  • location: cerebral hemispheres
  • stain: GFAP
  • histologic appearance: “psuedopalisading” pleomorphic tumor cells  
    • border central areas of necrosis and hemorrhage
  • gross appearance: can cross corpus callosum (butterfly glioma)
  • note: may arise de novo or progress from a lower grade astrocytoma
    • methylation of MGMT gene is a positive prognostic factor for survival 
• Meningioma 
  • prognosis: resectable
  • location: convexities of hemispheres , parasagittal region, olfactory groove
    • arises from arachnoid cells covering brain
  • histological appearance: spindle cells concentrically arrange in a whorled pattern  
    • psammoma bodies (laminated calcifications)
  • note: more common in women (due to estrogen receptors on tumor cells)
    • associated with neurofibromatosis
• Schwannoma
  • prognosis: good, resectable
  • location: often localized to CN VIII → acoustic schwannoma
    • usually found at cerebrellopontine angle 
    • can present with tinnitus, hearing loss
  • staining: S-100 positive 
  • histologic appearance: biphasic with hypercellular (Antoni A) and hypocellular (Antoni B) areas
  • note: bilateral schwannoma found in neurofibromatosis type 2
• Oligodendroglioma
  • prognosis: good, slow growing
  • location: most often in frontal lobes
  • histologic appearance: chicken-wire capillary pattern with “fried egg” cells 
    • round nuclei with clear cytoplasm 
• gross appearance: often calcified in frontal lobe

Childhood peak-incidence tumors

• Pilocytic (low-grade) astrocytoma
  • type: grade I astrocytoma
  • prognosis: benign
  • location: most often infratentorial
    • may be supratentorial (most commonly, craniopharyngioma)
  • stain: GFAP
  • histologic appearance: Rosenthal fibers  
    • eosinophilic corkscrew fibers 
  • gross appearance: cystic + solid, usually well-circumscribed
• Medulloblastoma
  • most common malignant intracranial tumor of childhood
  • prognosis: poor, highly malignant
    • form of primitive neuroectodermal tumor (PNET)
  • location: cerebellum
    • can compress 4th ventricle → hydrocephalus
  • histologic appearance: rosettes with small blue cells  
  • gross appearance: solid
  • note: radiosensitive
• Ependymoma
  • prognosis: poor
  • location: most commonly in 4th ventricle
    • can result in hydrocephalus
    • can also arise from cauda equina in adults
    • arises from ependymal cells 
  • histologic appearance: characteristic perivascular pseudorosettes 
• Hemangioblastoma (occurs typically in adults if no genetic predisposition as below)
  • location: cerebellar
  • histologic appearance: foamy cells and high vascularity
  • note: associated with von Hippel-Lindau syndrome when found with retinal angiomas
    • can produce EPO → secondary polycythemia
• Craniopharyngioma 
  • prognosis: benign
  • location: near sella turcica 
    • can present with optic chiasm compression → bitemporal hemianopia
      • confused with pituitary adenoma
    • derived from remnants of Rathke’s pouch 
  • gross appearance: calcification is common, tooth enamel-like
• Germinoma
  • prognosis: good
  • location:  pineal gland and suprasellar region 
    • derived from nests of embryonic cells arrested during their migration in fetal development
    • Pineal region: Parinaud syndrome (30-40% of cases) compression of tectum causes: paralysis of upward gaze, loss of light perception and accomodation, nystagmus, failure of convergence 
    • Suprasellar region: anterior hypopituitarism, precocious puberty, diabetes inspidius, visual disturbances
  • stain: AFP and b-HCG