The opinions expressed herein are those of the author(s), and are not necessarily representative of the Uniformed Services University of the Health Sciences (USUHS), the Department of Defense (DOD); or, the World Health Organization (WHO). Medicine is a constantly changing field, and medical information is subject to correction and revision. The reader is entirely responsible for verifying the accuracy and relevance of the information contained herein.

Last Revision: Friday, May 30, 1997 5:36:16 PM

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• PATHOLOGIST
  • LOW GRADE
  • HIGH GRADE
  
  
• RADIOLOGIST
  • NON-ENHANCING
  • ENHANCING
  
  
• NEUROSURGEON
  • Use the CUSA ("suckable")
  • Hard or Firm tumor ("non-suckable")

HISTOLOGIC MALIGNANCY

BIOLOGIC MALIGNANCY

CLINICAL MALIGNANCY

• CELLULAR ATYPIA
• MITOSES (Mitotic Index)
• INFILTRATION (lack of margination or encapsulation)
• NECROSIS (sign of uncontrolled growth)
• VASCULAR CHANGES (tumor neovascularity)

GLIOMA (ASTROCYTOMA)
GRADING SYSTEM:

• GRADE I - "BENIGN" or "Low-Grade"
• GRADE II - " "
• GRADE III - ANAPLASTIC, cellular atypia, etc.
• GRADE IV- MALIGNANT, NECROSIS !, Vascularity, Mitoses
  GLIOBLASTOMA MULTIFORME

NOTE: Numerous modifications exist, most into three grades, eg.: Low Grade (Benign), Anaplastic, and GBM (w/ NECROSIS).

HIGH-GRADE ASTROCYTOMAS
MEDIAN SURVIVAL:

• ANAPLASTIC (Grade 3/4) - 28Mos.

• GBM (Grade 4/4, has NECROSIS) - 8 Mos.

BIOLOGIC MALIGNANCY:

• RAPID GROWTH
• HEMORRHAGE, NECROSIS
• LOCAL EXTENSION
• HEMATOGENOUS DISSEMINATION

CNS NEOPLASM
Prognostic Factors

WHO Classification

• Defines Histologic Subtypes
• Grades Biologic Potential
• Allows International Cooperation

• Biological Potential
  
• Ascending Scale of Aggression
  I - IV

BIOLOGIC CORRELATION

• Low Grade Tumor
  • Long-Term Survival
    
  • Stable History (No Progression)

• Astrocytoma (Diffuse, fibrillary, protoplasmic, or gemistocytic astrocytes)
• Anaplastic Astrocytoma (AA)
• Glioblastoma Multiforme (GBM, Giant Cell GBM, Gliosarcoma)

Circumscribed Astrocytoma

• Pilocytic Astrocytoma (Juvenile - JPA)
• Subependymal Giant Cell Astrocytoma
• Superficial Cerebral Astrocytoma (SGCA, the intraventricular tumor of Tuberous Sclerosis)

• Pleomorphic Xanthoastrocytoma (PXA)

The New WHO
Classification of Brain Tumors

"BENIGN" ASTROCYTOMA

Two types:

• Low grade ("benign")
  Diffuse (Adults, cerebral hermisphere and brainstem)

• Low grade "special"
  Circumscribed (Children, characteristic location/morphology)

PATTERN ANALYSIS

Neoplasm

• "Special" astrocytomas, Astrocytoma of Young
• Well circumscribed (yet, no capsule)
• Various Locations (often characteristic)
• Do NOT change grade (except PXA)
• Do NOT spread along WM
• Constellation of findings correlates w/ Histology

PILOCYTIC ASTROCYTOMA

• Synonyms: Polar Spongioblastoma, Cystic Cerebellar Astrocytoma
• Cell of Origin: Astrocyte (bi-polar, hairlike)
• Associations: in ON (optic nerve) w/ NF-1
• Incidence: 3-6% of ALL Cranial, 32% of Child
• Age: 5-15 (Zulch 3-7)
• Sex: Slight F (11/9)
• Location: Cerebellum, Chiasm/Hypothal, Optic Nerve, Cerebral hemisphere, Cx spinal cord
• Treatment: Surgery, patience (radiation and chemotherapy uncommon)
• Prognosis: 77% at 5 yrs., many patients can be surgically cured

PILOCYTIC ASTROCYTOMA
Radiology

• Cerebellum, Diencephalon
  • rare in BS or Cerebrum
• Majority have significant "cyst"
  • "Cyst and Mural Nodule" appearnce is "Classic"
    • part of lining does NOT enhance
  • Nodule may be heterogeneous
  • Exceptional purely solid
• Nodule NOT hyperdense
• Calcification in 5-25%

Image Page 1

PATHOLOGY

• Biphasic pattern
  • dense pilocytic glia
  • Rosenthal fibers
  • loose microcystic areas
• No necrosis
• Low grade
• Abnormal capillaries allow enhancement, fluid

Image Page 2

Image Page 3

PILOCYTIC ASTROCYTOMA

• CEREBELLUM

• HYPOTHALAMUS

• CHIASM AND OPTIC NERVE

Image Page 4

PILOCYTIC ASTROCYTOMA
(Juvenile Pilocytic)

• Childhood, Young Adults
• Benign, no mitosis/necrosis
• Circumscribed - Enhancing
• Cyst Formation, Mural Nodule
• Cerebellum and Diencephalon (Optic tracts, Hypothalmus)

WHO GRADE I

• Circumscribed Astrocytoma
  • JPA (Pilocytic)
  • SGCA (Subependymal)
• Ganglioglioma
• Meningioma

ASTROCYTOMAS

• "SPECIAL" ASTROCYTOMA
  Circumscribed Growth:
  • Pilocytic
  • Subependymal Giant Cell
  • Pleomorphic Xantho.-

PLEOMORPHIC
XANTHOASTROCYTOMA

• Recently Described, Rare Variant of Astrocytoma
• Arises from Subpial Astrocytes
• Affects Superficial Cerebral Cortex and Meninges
• Temporal >Frontal > Parietal

PLEOMORPHIC
XANTHOASTROCYTOMA

• IMAGING:
  CT APPEARANCE:
  • Well-Circumscribed Hypodense or Cystic Mass
  • Often Isodense Solid Nodule That Intensely Enhances
  • May Mimic Juvenile Pilocytic Astrocytoma
  • Calcifications Rare

Image Page 5

PLEOMORPHIC
XANTHOASTROCYTOMA

MR APPEARANCE:

• Well-Circumscribed Mass of Variable Size
• Superficial Cortical Location
• T1: Low/Mixed Signal,
• T2: High/Mixed Signal
• Often with Cystic Component
• Solid Portion Intensely Enhances
• Adjacent Meninges May Enhance (Tail)
• Little or No Mass Effect

Image Page 6

ASTROCYTOMAS

• "ORDINARY" ASTROCYTOMA
  Diffusely Infiltrate Brain:
  • Fibrillary
  • Protoplasmic
  • Gemistocytic

ASTROCYTOMA:

DIFFUSE
(Fibrillary, protoplasmic, etc.)

Image Page 7

ASTROCYTOMA
Radiologic Grading

• TYPE 1 - (Benign, Grade 1-2)
  • Homogeneous
  • No Enhancement, No Edema
• TYPE 2 - (Anaplastic - Grade 3)
  • Variable Enhancement, Edema
• TYPE 3 - (Glioblastoma - Grade 4)
  • Heterogeneous (Necrosis, Blood)
  • Ring Enhancement, Edema

BENIGN ASTROCYTOMA:

• YOUNGER PATIENT
  • CHILDHOOD
  • Young Adults (20's - 40's)
• NL VESSELS (NO NEOVASCULARITY)
  • BBB INTACT
  • NO EDEMA
  • NO ENHANCEMENT
  • NO TUMOR VESSELS

Benign - Diffuse

HOMOGENEOUS
• NO NECROSIS
• NO HEMORRHAGE
• INCREASED WATER DARK on CT/T1W and BRIGHT on T2W
• MICROCYST >>> MACROCYST (macrocysts occur in JPA, etc.)

Image Page 8

MODES OF SPREAD

1. Natural passages
2. Along surfaces
3. Along tracts
4. Across the meninges

SPREAD ALONG TRACTS:

• CORONA RADIATA
• PEDUNCLES
• CORPUS CALLOSUM
• ANTERIOR COMMISURE
• ARCUATE FIBRES

Image Page 9

"MALIGNANT"ASTROCYTOMA:

• Older patient
  • 40's and up
  • exceptions (PNET)
• Abnl. Vessels (neovascularity)
  • BBB abnormality
  • vasogenic edema
  • contrast enhancement
  • irregular vessels, shunting, etc.
• HETEROGENEOUS
  • hemorrhage (old/new)
  • tumor necrosis
  • tumor itself

Image Page 10

GBM

• LOW DENSITY CENTER
  • variegated necrosis
• ENHANCING RIM
  • hypercellular, fleshy neoplasm
  • greatest neovascularity
• CORONA OF "EDEMA" (low density, dark T1W/bright T2W)
  • "edematous" white matter
  • areas of neoplastic infiltration

Image Page 11

GLIOBLASTOMA MULTIFORME
(Malignant Astrocytoma)

• Adults over 40 yrs.
• Malignant with mitoses, neovascularity
• Discrete ring-enhancing lesion
• Central necrosis, vasogenic edema
• Cerebral hemispheres (cross the corpus callosum)

*Radiology (1990) 174: 411-415

NEUROEPITHELIAL TUMORS
WHO Classification

• Astrocytic
• Oligodendroglial
• Ependymal
• Choroid Plexus Tumors
• Neuronal
• Neuronal Mixed w/ Glial
• Pineal
• Embryonal (PNET)

NEOPLASMS OF THE MENINGES
WHO Classification

1. MENINGIOMA:
   1. Meningioma (typical)
   2. Atypical Meningioma
   3. Anaplastic (Malignant) Meningioma
2. MESENCHYMAL (non-meningothelial)
3. Primary MELANOCYTIC Lesions
4. UNCERTAIN Origin
   1. Hemangiopericytoma
   2. Hemangioblastoma

MENINGIOMA
"Malignant Meningioma"

• Hemangio-Peri-Cytoma (HPC)
• Malignant Fibrous Histiocytoma (MFH)
• Papillary Meningioma
• "Benign" Metastasizing Meningioma

HEMANGIOPERICYTOMA
(HPC)

• Narrow dural base
  ("Mushrooming")
• No Hyperostosis, No Calcification
• Lobulated (not hemispheric)
• Internal Signal Voids (on MRI)
• Hypervascular on Angio

Image Page 12

DYSEMBRYOPLASTIC
NEUROEPITHELIAL TUMOR (DNT)

• IMAGING:
  • MR APPEARANCE
    • Focal cortical mass, usually temporal lobe
    • Hypointense on T1
    • Hyperintense on T2
    • Multinodular
      • Microcystic
      • Megagyric - may cause bony erosion
    • Ocassional Enhancement

DYSEMBRYOPLASTIC
NEUROEPITHELIAL TUMOR (DNT)

• IMAGING:
  • CT APPEARANCE
    • Hypodense Mass
    • No Edema
    • Rare Calcification
    • Calvarial Erosion
    • CT Normal in 10%

Image Page 13

The New WHO
Classification of
Brain Tumors

THE NEW WHO

• Biological Potential

• Ascending Scale of Aggression
  I - IV

CORRELATION

• Low Grade
  • Long-Term Survival
  • Stable Histology

WHO GRADE I

• Circumscribed Astrocytoma
  • JPA (Pilocytic)
  • SGCA (Subependymal)
• Ganglioglioma
• Meningioma

Other resources and references for the new WHO classification.

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