Ch 22 - CNS tumors Flashcards
What are gliomas?
- tumors of the brain parenchyma
- resemble the different types of glial cells
What are the types of the gliomas?
- astrocytomas
- oligodendrogliomas
- ependymomas
How is the consistency of ependymomas compared to astrocytoma and oligodendrogliomas?
the most common types are highly infiltrative or “diffuse gliomas,” including astrocytic and oligodendroglial, and mixed forms. In contrast, ependymomas tend to form solid masses
What are the most common types of astrocytomas?
- diffuse astrocytomas
- piloctic astrocytomas
Diffuse astrocytomas frequency?
- 80% of adult gliomas
- most frequent in the 4th through 6th decades of life
Where are the diffuse astrocytomas usually found?
cerebral hemispheres
What are the most common presenting signs and symptoms of diffuse astrocytomas ?
- seizures
- headaches
- focal neurologic deficits related to the anatomic site of involvement
Which groups are the diffuse astrocytomas stratified in to:
- well-differentiated astrocytoma (grade I/IV)
- anaplastic astrocytoma (grade III/IV)
- glioblastoma (grade IV/IV)
Read about diffuse astrocytoma:
page 842
Pilocytic astrocytoma:
- relatively benign tumors
- affect children and young adults
- often a cyst associated with the tumor, and recurrence from incompletely resected lesions is often associated with cyst enlargement, rather than growth of the solid component
Where are the pilocytic astrocytoma most commonly located?
- cerebellum may also involve: - third ventricles - optic pathways - spinal cord - occasionally cerebral hemispheres
Can the tumors that involve the hypothalamus be resected completely?
no. this is why they are problematic
pilocytic astrocytoma (morphology)
- often cystic, with a mural nodule in the wall of the cyst
- if solid: it is very well circumscribed - bipolar cells with long, thin “hair-like” processes that are GFAP-positive
- rosenthal fibers and microcysts are often present
- necrosis and mitoses are rare
Rosenthal fibers =
eosinophilic granular bodies
Oligodendroglioma frequency:
- 5%-15% of gliomas
- most commonly detected in the 4th and 5th decades of life
What are the complaints of patients with oligodendrogliomas?
- antecedent neurologic complaints
- seizures
Where are the oligodendrogliomas most commonly found?
- cerebral hemispheres, mainly in the frontal and temporal lobes
What are the most common genetic findings in patients with oligodendrogliomas?
the most common genetic findings are deletions of chromosomes 1p and 19q, alterations that typically occur together
- they are usually highly responsive to chemotherapy and radiotherapy
Oligodendrogliomas (morphology):
- gelatinous, gray masses
- may show cysts, focal hemorrhage, and calcification
- sheets of regular cells with spherical nuclei containing finely granular-appearing chromatin surrounded by clear halo of cytoplasm
- typically contain a delicate network of anastamosing capillaries
- calcification present in 90% of the tumors
Describe anaplastic oligodendrogliomas:
- aggressive subtype
- higher cell density
- nuclear anaplasia
- mitotic activity
Where does the ependymoma most often arise?
next to the ependymal lined ventricular system, including the central canal of the spinal cord
Where does the ependymoma most likely occur during the first 2 decades of life?
near the fourth ventricle
What is the most common location of ependymoma in adults?
the spinal cord
How are the ependymoma in the fourth ventricle?
- solid or papillary masses extending from the ventricular floor
- cells with regular, round to oval nuclei
- abundant granular chromatin
- dense fibrillary background between the nuceli
- rosettes canals or perivascular pseudorosettes (more on page 844)
Describe anaplastic ependymoma:
- increased cell denstiy, high mitotic rates, necrosis, and less evident ependymal differentiation
What is central neurocytoma?
- low-grade neoplasm
Where are central neurocytoma found?
- within and adjacent to the ventricular system (most commonly the lateral or third ventricles)
What characterizes central neurocytoma?
- evenly spaced, round, uniform nuclei and often islands of neuropil
Neuropil:
a dense network of interwoven nerve fibres and their branches and synapses, together with glial filaments.
What are gangliogliomas?
- tumors mixed with a mixture of glial elements, usually low-grade astrocytoma, and mature-appearing neurons
- slow-growing
- seizures
Dysembryonic neuroepithelial tumor:
- low-grade childhood tumor
- grows slowly
- seizure disorder
Where are the dysembryonic neuroepithelial tumor typically located?
- superficial temporal lobe and consist of small round neuronal cells
- well differentiated “floating” neurons within pools of mycopolysaccharide-rich myxoid fluid
What is the most common embryonal (primitive) neoplasms?
medulloblastoma, accounting for 20% of pediatric brain tumors.
Where does the medulloblastoma predominantly occure?
in children and exclusively in the cerebellum
Are neuronal and glial markers almost always expressed in medulloblastoma?
yepp
Is medulloblastoma exclusively readiosensitive?
yepp
Primitive neurectodermal tumors (PNETs):
tumours similar to medulloblastoma and with poor degree of differentiation and found elsewhere in the nervous system
Where are medulloblastoma located in children?
in the midline of the cerebellum
In who does the lateral tumors occur more often in?
adults
Medulloblastoma (morphology):
- well circumscribed
- gray, and friable
- may be seen extending to the surface of the cerebellar folia and involving leptomeninges
- extremely cellular, with sheets of anaplastic (“small blue”) cells
focal neuronal differentiation is seen in the form……
of the Holmer Wright or neuroblastic rosette
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