BrainTF1-Astrocytoma

Clinical Profile

Findings

Discussion

Pathology

On MRI

Differential Diagnosis

Suggested Reading

Clinical Profile:

H/O left hemiparesis since 15 days in a young patient.

Findings:

There is evidence of a hypointense lesion which turns hyperintense on the proton, T2W and FLAIR images in the right fronto-parietal region. Within this lesion is noted a well defined area which is mildly hyperintense to CSF and would represent a cystic or necrotic component. On contrast administration the lesion is seen to enhance intensely. The cystic component does not show any contrast uptake. There is indentation upon the body of the right lateral ventricle.

Discussion:

Patients usually present with seizures or features which may be related to the location of the lesion. They may present with focal neurological deficits or symptoms related to increased intracranial pressure (increasing headaches - more so in the morning, nausea, vomiting and visual symptoms).

Astrocytic brain tumours may either be diffuse or infiltrative and localized or circumscribed. They account for 20% to 30% of the tumours in the glioma group. They arise due to a proliferation of astrocytes (more often fibrillary than protoplasmic or gemistocytic).

Diffuse:

• Astrocytoma:
  Relatively benign. Located commonly in the cerebral  hemispheres in adults. May be seen in the posterior fossa in younger patients. They expand the brain parenchyma and may have microcystic formation and occasional calcification. 10% dedifferentiate into more malignant forms.                  
• Anaplastic Astrocytoma:
  Intermediate form. Arise de novo or dedifferentiate from an astrocytoma. Located commonly in the cerebral  hemispheres in adults. May be seen in the brainstem in children. May show necrosis, hemorrhage and vasogenic edema.
• Glioblastoma Multiforme:
  Highly malignant. Arise de novo or dedifferentiate from an astrocytoma. Located commonly in the cerebral  hemispheres in adults. Usually in the frontal or temporal lobes. Butterfly pattern may be noted. Central necrosis, hemorrhage, hypervascularity and extensive white matter edema are noted. May be seen in the posterior fossa in younger patients. Occasionally multicentric.
• Gliomatosis Cerebri:
  Diffusely infiltrative glial tumour with relative preservation of the adjacent neural structures. Occasionally leptomeningeal. Involve grey and white matter with extensive demyelination.

Localized:

• Pilocytic Astrocytoma:
  In children. Relatively benign. Commonly in the cerebellar hemispheres. When supratentorial, are seen in the diencephalon or optic nerves. Occasionally in the cerebral hemispheres. May dedifferentiate into more malignant forms. Usually have a cystic component with a vascular tumour nodule in the cyst wall. The overlying leptomeninges may show a fibroblastic reaction. Known to be associated with neurofibromatosis type 1. 
• Pleomorphic Xanthoastrocytoma:
  Superficially located, usually within the temporal lobe in young adults. May have a cystic component. 10% to 25% dedifferentiate into more malignant forms.                  
• Subependymal Giant Cell Astrocytoma:
  Is a parenchymal lesion which protrudes into the ventricle from a subependymal location. Usually located at the foramen of Monro in patients with tuberous sclerosis. Commonly calcified.

• Astrocytoma:
  Usually homogenous lesions and are hyperintense on the proton, T2W and FLAIR images (occasionally heterogeneous) with minimal perilesional edema, if any. Focal cystic changes may be seen (Iso to hyperintense to CSF. Fluid-debris levels may be seen). Cortical thickening may be seen.  Focal parenchymal enhancement may be seen.
• Anaplastic Astrocytoma:
  Usually heterogeneous with perilesional edema. Cystic changes may be seen. Variable enhancement pattern - nodular, homogenous or ring-like.
• Glioblastoma Multiforme:
  Poorly defined hyperintense lesions on the proton, T2W and FLAIR images. Tend to show necrosis, hemorrhage and hypervascularity (punctate or curvilinear signal voids). Extensive white matter edema and mass effect are seen. Corpus callosum may be involved. Usually show an irregular pattern of enhancement. May invade the meninges or disseminate via the subarachnoid space.
• Gliomatosis Cerebri:
  Marked parenchymal involvement. Seen as poorly defined hyperintense lesions the proton, T2W and FLAIR images. Enhancement is uncommon.
• Pilocytic Astrocytoma:
  Well defined lobulated mass. The solid component is either isointense or hyperintense to brain parenchyma on the proton, T2W and FLAIR images. The cystic component is isointense or hyperintense to CSF. The solid component usually shows partial but intense enhancement. Perilesional edema is rare.
• Pleomorphic Xanthoastrocytoma:
  Seen as a superficial solid mass, usually with a cyst deep to the solid portion. A site of dural attachment is commonly seen. They are isointense to grey matter on the T1W images and mildly hyperintense on the proton, T2W and FLAIR images. Solid component usually enhances.
• Subependymal Giant Cell Astrocytoma:
  Commonly seen as a bulky mass at the foramen of Monro. Well defined with occasional infiltration of the brain parenchyma. Variable signal on the T1W images and mildly hyperintense on the proton images. They may be relatively hypointense to CSF on the heavily T2W images. Calcium is usually hypointense. These lesions invariably enhance.

Suggested Reading:

1. Atlas SW, Ehud L: Intra-Axial Brain Tumors. In: Atlas SW: Magnetic Resonance Imaging of the Brain and Spine, Lippincot-Raven, pp:315-422, 1996.
2. Tumors of the Central Nervous System. In: Poirier J, Gray F, Escourolle R: Manual of Basic Neuropathology, W.B. Saunders, pp: 17-56, 1990.