MORPHOLOGYHemangioblastoma, theprincipalneurologicmanifestationofthedisease,isahighlyvascularneoplasmthatoccursasamuralnoduleassociatedwithalarge,fluid-filledcyst.Theseoccurmostcommonlyinthecerebellum,butcanbefoundalongthespinalcordandintheretina,andrarelyatothersitesinthebrain.Onmicroscopicexamination,thelesionconsistsofnumerouscapillary-sizedorsomewhatlargerthin-walledvesselsseparatedbyinterveningstromalcellswithavacuolated,lightlyPAS-positive,lipid-richcytoplasm.Thesestromalcellsexpressinhibin,amemberoftheTGF-β family,whichservesasausefuldiagnosticmarker.
TumorsoftheCNSmayarisefromthecellsofthecoverings(meningiomas),thebrain(gliomas,neuronaltumors,choroidplexustumors),orotherCNScellpopulations(primaryCNSlymphoma,germcelltumors),ortheymayoriginateelsewhereinthebody(metastases).
Evenlow-gradeorbenigntumorscanhavepoorclinicaloutcomes,dependingonwheretheyoccurinthebrain.
Distincttypesoftumorsaffectspecificbrainregions(e.g.,cerebellumformedulloblastoma,anintraventricularlocationforcentralneurocytoma)andspecificagepopulations(medulloblastomaandpilocyticastrocytomasinpediatricagegroups,andglioblastomaandlymphomainolderpatients).
Glialtumorsarebroadlyclassifiedintoastrocytomas,oligodendrogliomas,andependymomas.Increasingtumormalignancyisassociatedwithmorecytologicanaplasia,increasedcelldensity,necrosis,andmitoticactivity.
Metastaticspreadofbraintumorstootherregionsofthebodyisrare,butthebrainisnotcomparablyprotectedagainstthespreadofdistanttumors.Carcinomasarethedominanttypeofsystemictumorsthatmetastasizetothenervoussystem.
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Infections of the Nervous System