Saturday, June 16, 2012

CNS TUMORS



Epidemiology
 Half of all brain and spinal cord tumors are metastatic
 Most frequent primary CNS tumors: Meningiomas
                                                                Glioblastoma multiforme

Clinical manifestations
Headache, often worse at night or early morning
Seizures, with tumors involving cerebral cortex
Mental changes (e.g., deficits in memory, concentration, reasoning, etc.)
Focal neurological symptoms, related to involvement of specific brain regions
Symptoms related to increased intracranial pressure
i. Presence of a space-occupying mass within the cranial cavity
ii. Blockage of CSF flow
iii. Edema around the tumor (peri tumoral edema)


Special features of brain tumors
i. Malignant CNS tumors do not metastasize outside the cranial cavity.
ii. Clinical consequences depend on infiltrative behavior and location.

Differences Between Primary and Metastatic Tumors


Astrocytomas

a. Originate from astrocytes and exhibit
i. Fibrillary background
ii. Immunoreactivity for glialfibrillary acidic protein (GFAP)
iii. Diffuse (ill-demarcated) pattern of growth

a. Fibrillary astrocytomas
 Grading is important for both prognosis and treatment. Most frequent systems
 Four grades based on nuclear atypia (pleomorphism),
-mitoses, necrosis, and vascular endothelial hyperplasia (VEH)

 Grade 1-2 astrocytomas are well differentiated astrocytomas
 Grade 3 astrocytomas are anaplastic astrocytomas
 Grade 4 astrocytomas are called glioblastoma multiforme (GBM)

 GBM is the most cormmon CNS primary malignancy


Most common location: white matter
Histology: marked nuclear atypia, mitoses, necrosis, and VEH 

Characteristic histo pathological feature: pseudopalisading necrosis
 VEH is often florid, giving rise to glomeruloid formations



Glioblastoma multiforme has a tendency to cross the midline
by involving the corpus  callosum, hence k/a"Butterfly glioma"


Anaplastic astrocytoma showing marked nuclear pleomorphism


b. Pilocytic astrocytoma
 Benign astrocytic tumor of children and young adults

 Locations: posterior fossa (cerebellum) and diencephalon

 Often presents as a cystic lesion with a mural nodule



Histology: 
-spindly neoplastic astrocytes with long bipolar processes
-tumors rich in Rosenthal fibers (thick corkscrew-like eosinophilic structures, which derive from hypertrophic processes of astrocytes)

Favorable prognosis for posterior fossa tumors


Oligodendroglioma
 Glioma of oligodendroglial origin
 Occurs in 30- to 50-year-old patients

Location: white matter of cerebral hemispheres adjacent to neocortex


Often manifests with seizures

Characteristic histopathology
i. Neoplastic cells are similar to oligodendroglia
ii. Pronounced perinuclear halo: "fried-egg" appearance


iii. Prominent capillary network in a chickenwire pattern

Slow-growing tumors that allow long survival (average 5-10 years)
Recur after surgery and degenerate into high-grade gliomas over time


Ependymoma
Glioma of ependymal origin

 Location
1. Children: fourth ventricle
ii. Adults: lateral ventricle or spinal canal

Gross appearance: circumscribed tumors with papillary architecture


Histology: neoplastic cells resemble ependymal cells. Characteristic features:
i. Ependymal rosettes


ii. Perivascular pseudo rosettes


Often presents with obstructive hydrocephalus, when present in the fourth ventricle
Tend to recur after surgery and acquire more aggressive behavior


Meningioma
 Originates from meningothelial cells of the arachnoid
 Tumors of adulthood (women> men), rare in children
May develop at any meningeal site. Most frequent are dural convexities

Gross: attached to the dura, 
pushes underlying brain 
without invasion
Microscopic
i.Spindle-shaped cells with indistinct borders (syncytial)
ii. Cells arranged in whorls or fascicles
iii. Psammoma bodies frequent



Generally, good prognosis
Tumors in some location may not be amenable to complete resection


Primitive neuroectodermal tumors (PNET)
Highly undifferentiated; originate from a primordial neuroglial precursor
Variably named, depending on location in the brain
Most frequent PNETs: medulloblastoma and 
                                       retinoblastoma


All PNETs share the following features:
i. Develop in children
ii. Histology: blue, small, round cell tumors, with pseudorosettes
iii. Highly aggressive but responsive to radiation therapy
.


Histo:

Medulloblastoma arises in the cerebellar vermis (midline location)

i. Grows rapidly and spreads through CSF
ii. Resection and radiation therapy allow 5-year survival of 75%.
Schwannoma

Originates from Schwann cells of cranial or spinal nerves
Associated with NF type II
Most frequent location: eighth cranial nerve
                                         cerebellopontine angle(CPA)
 Manifests characteristically with loss of hearing and tinnitus


Histology
i. Spindle cells arranged in hypercellular  Antoni A areas, alternating with hypocellular  Antoni B areas
ii. Verocay bodies:  parallel rows of neoplastic Schwann cells 




Verocay bodies

Neoplastic cells are immunoreactive  for a protein called S-100
Good prognosis after surgical resection


Craniopharyngioma

Arises from the remmanants of Rathke’s pouch
Patients affected are usually children or young adults
Location: within the suprasellar/diencephalic region 


Gross: craniopharyngiomas are cystic or partially-cystic with solid areas. 


Histo:  nesting of squamous epithelium bordered by radially arranged cells.
           resembles adamantinoma, the most common tumor of the tooth


Contains deposits of calcium evident on x-rays
Benign but tends to recur after resection


T/T:
   Trans-sphenoidal resection of the tumor.


Investigations of Brain tumors:
1. CT/MRI Head
       allows localization of the tumor.
       MRI has value in investigation of posterior fossa tumors and brain stem

2. CXR:
    provides evidence of primary lung tumor

T/t

1.Medical: Relief of ICP is reqd. when surgery is not possible or
  when life is threatened before diagnosis is revealed.
 Dexamethasone is used.
 

2. Surgical:
    Main stay of t/t

3. Radiotherapy and Chemotherapy

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