Neoplasms Of The Nervous System

Neoplasms Of The Nervous System Introduction Primary (3/4) or metastatic• of deaths from malignancy 2% • Second most common neoplasm in children (20%) after leukemia • ((more likely arise in posterior fossa :CNS neoplasms are different from neoplasms of otherorgans • Criteria of malignancy are different & less evident○ Patten of growth of low-grade tumors may still include ○ infiltration of large regions of brain  serious clinical effects & poor prognosis Even benign ones may cause death due to compression of vital ○ ”structures “Location of the tumor is important Malignant neoplasms rarely metastasize outside of CNS ○ The subarachinoid space provides a pathway for spread ○ Ability to surgically resect infiltrating glial tumors without ○ compromising neurologic functions is limited

Classification of Primary CNS Tumors :”A. Gliomas “derived from glial cells :Astrocytoma .1

:Can be classified as ( Pilocytic astrocytoma (WHO- I.1 :Fibrillary “infiltrating or diffuse” astrocytomas .2 ( Low grade astrocytoma (WHO- II○ ( Anaplastic astrocytoma (WHO- III ○ ( High grade “glioblastoma multiforme” (WHO- IV ○ Pilocytic Astrocytoma.1 Typically occur in children & young adults Common sites: cerebellum, 3rd ventricle & optic nerve Relatively benign & have excellent prognosis if resectable :Gross Well-defined͵ Often cystic with small mural nodule in wall͵ :Microscopic ”Bipolar cells with hairlike processes “pilocytic͵ GFAP +ve͵ Rosenthal fibers͵ Eosinophilic granular bodies͵ Microcystic areas͵ No mitosis or necrosis͵ Fibrillary Astrocytomas.1 Account for 80% of adult 1ry brain tumors Most frequent in 4th-6th decades Mainly in cerebral hemispheres Most common presenting symptoms: seizures, headaches & focal neurologic deficits They have tendency to become less well differentiated over time 1

Prognosis depends on age, location & histological grade “GBM has a ”very poor prognosis Rx: Resection if possible + radio & chemo mean survival of 8-10 months. <10% are alive after 2 yrs Low-Grade Astrocytoma Poorly defined & infiltrative͵ Expand , distort parenchyma & obliterate grey/white matter͵ boundaries Infiltration beyond grossly evident margins is always present͵ Transition between neoplastic & normal tx is indistinct͵ Increased numbers of irregularly distributed, mildly atypical &͵ pleomorphic astrocytes with intervening background of fine GFAP +ve (astrocytic cell processes (fibrillary appearance͵ Anaplastic astrocytoma demonstrates marked cellularity with marked pleomorphism &͵ increased mitotic activity Glioblastoma Multiforme Gross: Infiltrative with irregular areas of Hg, necrosis & cystic changes• Micro: Serpentine necrosis with pseudo-palisading nuclei & vascular or• endothelial cell proliferation

:Oligodendroglioma .2

of gliomas 5-15% (Occur in adults (4th & 5th decade Occur in cerebral hemispheres mainly in white matter :Can be subdivided into Low-grade (High-grade (anaplastic Prognosis is better than astrocytomas, anaplastic is worse Rx: Surgery + chemo + radio  average survival of 5-10 yrs Most common genetic abnormality is loss of heterozygosity of chromosome 1p &19 q  consistent & long-lasting Rx response

Gross Gelatinous, grey, infiltrative mass͵ May show cysts, focal hemorrhage & calcification͵ Calcification may be seen in up to 90% of tumors &range from͵ microscopic foci to massive depositions They are helpful clues for radiologic Dx͵ microscopic Sheets of regular cells with rounded, uniform nuclei which are͵ surrounded by a clear perinuclear cytoplasmic halo Typically contains delicate network of anastomosing capillaries͵ Anaplastic tumors: increased cellularity, pleomorphism, mitosis &͵ necrosis Calcification

:Ependymoma .3

:In children In first 2 decades of life Account for 5-10% of 1ry brain tumors in this age group Typically occurs near 4th ventricle

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:In adults Occurs most commonly in spinal cord Mainly in setting of neurofibromatosis type2 CSF dissemination is common The clinical outcome of completely resected supratentorial & spinal ones is better than for those in posterior fossa :Gross In 4th ventricle they are typically solid or papillary masses ͵ extending from the ventricluar floor :Microscopic Perivascular pseudorosettes: Processes of cells are radiating around͵ blood vessels Ependymal rosettes: Processes of cells are radiating around lumina͵

: ” B. Primitive Neuroepithelial Neoplasms “PNET

Are composed of embryonal “primitive” cells Occur predominantly, but not exclusively in children :They include *  Medulloblastomas  Pineoblastoma  Ependymoblastoma  Medulloepithelioma *  Neuroblastoma

Medulloblastoma (Is derived from primitive neuroectodermal cells (undifferentiated Accounts for 20% of pediatric brain tumors Occurs predominantly in children (in first 2 decades) and exclusively (in the cerebellum (midline vermis In adults “rare” is often found in lateral cerebellar hemispheres ”May lead to hydrocephalus “if obstructing ventricles Frequently disseminate through CSF Highly malignant with poor prognosis if untreated, but with multimodality therapy "radiosensitive” 5ys survival rate may reach 75% :Gross Well circumscribed͵ Friable & gray͵ :Micro Extremely cellular with sheets of anaplastic small blue “primitive”͵ cells with small Homer Wright rosettes “cells are arranged around a central fibrillary core”. Mitoses are abundant

:C. Neuronal Neoplasms

:They include  Gangliocytoma  Ganglioglioma ( Dysembryoplastic neuroepithelial tumor (DNT  Central Neurocytoma Occur mainly in children & young adults Almost all are low-grade 3

Important causes of seizures

: D. Meningiomas

Are predominantly benign Are derived form meningothelial cells that invest arachnoid Are usually attached to dura & are outside brain parenchyma May occur in cranial vault or spinal cord Occur mainly in adults, F > M Multiple meningiomas, especially in association with 8th nerve schwannomas or glial tumors should raise suspicion of NF-2 of meningiomas not associated with NF2 still have mutations 50% ~ (in NF2 gene on long arm of chromosome 22 (22q

:Gross Well-defined, firm & lobulated͵ Attached to dura mater͵ Sharp interface with adjacent brain / spinal cord , easily separated͵ Extension into overlying bone maybe present͵ :Microscopic Syncytial meningiomas = composed of compact cellular whorls.1 Fibroblastic meningiomas = composed of elongated cells with.2 interspersed collagen Transitional meningiomas = share features of syncytial &.3 fibroblastic types Secretory meningiomas = has PAS +ve intracytoplasmic droplets &.4 intracellular lumina byEM Microcystic meningiomas = Has loose & spongy appearance.5 Psammomatous meningioma = numerous psammoma bodies.6

:(E. Germ Cell Tumors (GCTs

Teratomas* & other germinomas Occur along midline, most commonly in pineal & suprasellar region occur during 1st two decades 90% Tumors in pineal region show a strong male predominance Histologic classification is the similar to testicular tumors. However, CNS germinoma is the counterpart of testicular seminoma

:(F. Primary Brain Lymphoma (PBL

Account for 2% of extranodal lymphomas & 1% of intracranial tumors Majority are diffuse large B-cell lymphomas It is the most common CNS neoplasm in immunosuppressed (AIDS & transplant) patients. In these pts lymphomas are nearly all caused by EBV In nonimmunosupressed populations the incidence increases after 60 years of age Often multifocal within CNS Nodal, extranodal & BM involvement is rare & late complication Is an aggressive disease with relatively poor response to chemoRx as compared with peripheral lymphomas

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Metastatic Tumors Accounts for ¼ of intracranial tumors Brain is a common site for mets Occur mainly in elderly The 5 most common 1ry sites: lung, breast & malignant melanoma, .GIT & kidney Account for 80% of all cases Meninges are also a frequent site of involvement by mets :Morphology Solitary or multiple Usually are well demarcated, have sharp interface with adjacent parenchyma & roughly spherical Often present at gray matter-white matter junction Usually surrounded by a zone of edema & reactive gliosis Tumors - Summary Tumors of the nervous system may arise from the cells of the coverings (meningiomas), from cells intrinsic to the brain (gliomas, neuronal tumors, choroid plexus tumors), or other cell populations within the skull (primary CNS lymphoma, germ-cell tumors), or they may spread from elsewhere in the body (metastases). Even low-grade or benign tumors can have a poor .clinical outcome depending on wherein the brain they occur Glial tumors are broadly classified into astrocytomas, oligodendrogliomas, and ependymomas. Increasing tumor malignancy is ,associated with more cytologic anaplasia increased cell density, necrosis, and mitotic activity. The most aggressive and poorly differentiated glial tumor is glioblastoma; it contains anaplastic astrocytes and shows .striking vascular abnormalities Metastatic spread of brain tumors to other regions of the body is rare, but the brain is not comparably protected against spread of tumors from elsewhere. Carcinomas are more commonly metastatic to the nervous system than lymphoid malignancies; sarcomas infrequently metastasize to the brain

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