Last revised 28 May 2008
Last major update January 2006
Copyright (c) 2005-2008, PathologyOutlines.com, Inc.
See also Central nervous system-nontumor (future topic), Pituitary (future topic)
Bold and underlined topics are hypertext links
Table of contents for Central Nervous System-tumor
CNS cysts: general, arachnoid, choroid plexus, colloid, dermoid, enterogenous, ependymal, epidermoid, glial, meningeal, neuroepithelial, pineal, simple, syrinx
Tumors: general, approach to diagnosis, WHO classification
Glial tumors
Glioma-general, post-radiation
Astrocytic tumors: general, cystic, granular cell, WHO grading, pilocytic, diffuse, protoplasmic, gemistocytic, anaplastic, glioblastoma, gliosarcoma, pleomorphic xanthoastrocytoma, subependymal giant cell
Oligodendroglial tumors: oligodendroglioma, anaplastic oligodendroglioma
Mixed gliomas: oligoastrocytoma and anaplastic oligoastrocytoma
Ependymal tumors: ependymoma, anaplastic ependymoma, myxopapillary ependymoma, subependymoma
Neuroepithelial tumors of uncertain origin: astroblastoma, chordoid glioma, gliomatosis cerebri
Neuronal and mixed neuronal-glial tumors: ganglion cell tumors-general, gangliocytoma, ganglioglioma, desmoplastic infantile astrocytoma/ganglioglioma, dysembryoblastic neuroepithelial tumor, central neurocytoma, cerebellar liponeurocytoma, extraventricular neurocytoma, papillary glioneuronal tumor, paraganglioma
Nonglial tumors
Embryonal tumors: ependymoblastoma, medulloblastoma, supratentorial PNET, atypical teratoid/rhabdoid tumor, medullomyoblastoma, medulloepithelioma
Choroid plexus tumors: general, papilloma, carcinoma
Pineal tumors: pineal gland-normal, tumors-general, papillary tumor, pineoblastoma, pineocytoma, pineal parenchymal tumor of intermediate differentiation
Meningeal tumors: meningioma, WHO grading, anaplastic, atypical, chordoid, clear cell, invasive, papillary, rhabdoid, secretory; meningioangiomatosis, hemangiopericytoma, melanocytic tumors / melanoma
Germ cell tumors: general, germinoma, embryonal carcinoma, yolk sac tumor, choriocarcinoma, teratoma
Tumors of the sellar region: craniopharyngioma, ganglion cell tumor, pituicytoma, pituitary adenoma, pituitary carcinoma, spindle cell oncocytoma
Lymphoma and other hematopoietic lesions: primary CNS lymphoma, secondary CNS lymphoma, post-transplant lymphoproliferative disorders, anaplastic large cell, angiotropic, diffuse large B cell lymphoma, Erdheim-Chester disease, histiocytic lymphoma/sarcoma, Hodgkin’s, inflammatory pseudotumor, Langerhans cell histiocytosis, leukemia, lymphomatoid granulomatosis, plasma cell granuloma, Rosai-Dorfman
Mesenchymal and other tumors: chondroma, chondrosarcoma, chordoma, epithelioid hemangioendothelioma, fibro-osseous lesions, hemangioblastoma, lipoma, MPNST, neurofibroma, sarcoma, schwannoma, solitary fibrous tumor, textiloma
Metastatic tumors to brain/spinal cord: general, metastatic carcinoma, metastatic choriocarcinoma, metastatic melanoma, paraneoplastic syndromes
Miscellaneous: intraoperative consultation, procedures, grossing, features to report, staging, autopsy
Click here for CNS-nontumor (future topic)
Primary references
American Journal of Surgical Pathology (AJSP), January 1999 to January 2006
Archives of Pathology and Laboratory Medicine (Archives), January 1999 to December 2005
Human Pathology, January 1999 to December 2005
Modern Pathology, January 1999 to December 2005
Sternberg, S: Diagnostic Surgical Pathology (4th Ed); Lippincott Williams & Wilkins, 2004
Websites: Akron Children’s Hospital, Atlas Interactif de Neuro-Oncologie, Virginia Commonwealth University
Journal search terms: brain, CNS, meninges, spinal cord
Please refer to these primary references for more detailed discussions and photographs
CNS cysts
No solid nodule of tissue
Tumors that commonly are cystic: pilocytic astrocytoma, craniopharyngioma, ganglioglioma, hemangioblastoma, occasionally metastatic carcinoma
Specimen preparation: save portion for EM; fix tissue and then cut sections of cyst wall; submit as many sections as possible to rule out neoplasm
Micro: no solid nodule of tissue; cyst wall may contain astrocytes, Rosenthal fibers, glial fibrils
DD: abscess (granulation tissue and fibrosis, inflammation); tumors with cystic areas (pilocytic astrocytoma: often in cerebellum; hemangioblastoma: vascular, lipid+, factor VIII+, reticulin outlines each cell), meningeal cyst (on spinal surface, syncytial type cells, collagen+), pineal cyst
Subdural or subarachnoid cyst containing CSF
1% of intracranial masses; protrude towards brain or spinal cord; often in middle fossa near temporal lobe
Congenital lesions that arise from split in leptomeninges, also due to trauma or leptomeningitis
Treatment: surgery if symptomatic
Radiologic images: MRI - spinal cord cyst; CT - left temporal lobe cyst
Gross: variable size, but may be vary large; thin transparent wall with clear, colorless fluid; cyst is distinct from leptomeninges and dura
Gross images: cyst of left temporal lobe
Micro: thinner wall than epidural cyst; lined by connective tissue and meningothelial cells
Micro images: thin cyst wall; meningothelial cells
May be present throughout ventricular system, but usually in glomus of lateral ventricles
More frequent in children than adults
Contain CSF
Present in 1-2% of fetuses, <1% associated with trisomy 18
Radiologic images: MR shows small cyst; choroid cyst
Case reports: 53 year old woman with small lesion at foramen of Monro (Am J Neuroradiology 2002; 23:841)
Gross images: cyst at foramen of Monro
Micro: wall composed of connective tissue and epithelial cells
Positive stains: transthyretin
Uncommon; probably due to maldevelopment
Usually ages 20-50 years in third ventricle near foramen of Monro
May cause intermittent positional headaches, hydrocephalus and rarely be fatal if it blocks foramen of Monro
May rupture and mimic abscess or ventriculitis unless colloid is identified
Case reports: 36 year old woman with AIDS, headache and nuchal rigidity (Am J Neuroradiology 2000;21:1470)
Gross: up to 3-4 cm; round, unilocular with thin wall; cyst content after fixation is gray with consistency of soft cartilage
Gross images: colloid cyst #1; #2; #3 in third ventricle; #5; obstruction of foramen of Monro by gelatinous cyst
Micro: fibrous wall lined by simple columnar epithelium (also flattened, cuboidal, squamous) with variable cilia or mucin; also colloid or ghost cells
Micro images: lined by cuboidal or columnar epithelium; epithelium with ciliated and goblet cells resting on collagenous tissue; myelin stain
Positive stains: epithelium - keratin, mucin; contents are PAS+ and Alcian blue+
Negative stains: epithelium - GFAP, vimentin, neurofilament
DD: depending on location enterogenous cyst, ependymal cyst, Rathke cleft cyst
References: eMedicine
Uncommon; much less common than epidermoid cyst
Midline cerebellum, fourth ventricle, skull, spinal dura, cauda equina
May involve CNS or meninges
May derive from embryonic inclusions of skin at time of closure of neural groove at 3-5 weeks of gestation
May have sinus tract in nasofrontal or occipital regions
Benign; may rupture and cause chemical meningitis and inflammation resembling abscess
Radiologic images: various images
Gross: well defined, round/oval, opaque or pearly; variable size, variable wall thickness; contains greasy material with variable hair; may have solid components
Gross images: cyst from cerebellum with hair and sebaceous material
Micro: fibrous wall lined by keratinizing squamous epithelium with skin adnexa, cyst contains squames, hair, sebum; hair shafts are highlighted with polarized light; rupture may cause granulomatous inflammation with foreign body giant cell reaction
DD: cystic teratoma
References: eMedicine
Also called neurenteric cyst
Rare, benign; probably due to maldevelopment
Usually in spinal cord (lower cervical and upper thoracic) presenting with spinal cord or cranial nerve compression; rarely intracranial
Usually intradural or subdural; intradural cysts are usually attached to spinal cord
Infants, children and adults
Cells resemble bronchial epithelium (Appl Immunohistochem Mol Morphol 2004;12:230)
Treatment: complete excision; occasionally is adherent to adjacent structures
Case reports: 78 year old man with cyst in front of medulla (Am J Neuroradiology 2001;22:496), intramedullary cyst of spinal cord presenting during pregnancy (J Neurol Neurosurg Psychiatry 2001;71:528), 43 year old man with cystic mass at cerebellopontine angle (Archives 2003;127:e45)
Gross: usually 1 cm or less
Micro: columnar epithelium with mucin (usually without cilia), resting on collagen layer; resembles intestinal or respiratory epithelium; goblet cells often present; may have squamous metaplasia
Micro images: (1) single layer of ciliated columnar epithelium; (2) figure 1: MRI shows mass at cerebellopontine angle; 2: cyst lining has single or pseudostratified columnal epithelium with focal squamous metaplasia; 3: cells have prominent apical cilia with basal nuclei but no atypia
Positive stains: Alcian blue, mucicarmine, PAS, EMA, CK5/6 (basal cells), CEA
Negative stains: GFAP, S100, NSE, vimentin
EM: well developed stereocilia, distinct basal cells, thin basement membrane
DD: colloid cyst (in third ventricle), ependymal cyst (abuts onto gliotic neuropil, GFAP+), cystic tumors
Rare; affects brain and spinal cord; usually not midline
Not in communication with ventricle or CSF spaces
Rarely ruptures and causes meningitis
Radiologic images: frontal ependymal cyst
Case reports: 15 year old boy with recurrent, intramedullary cyst at C2-C3 (Neurology India 2003;51:111-free full text)
Gross: resemble arachnoid cyst
Gross images: ependymal cyst
Micro: ciliated columnar cells with underlying fibrosis or fibrillary glia; may have ependymal-like cells or cilia; no mucin production
Micro images: cyst wall is lined by ependymal cells with focal multilayering
Positive stains: GFAP
EM: neuroepithelial origin
Also called epidermoid or epidermoid tumor
More common than dermoid cyst (1% of intracranial masses)
Occurs at cerebellopontine angle, temporal lobe, spinal dura, pineal gland, sella, brainstem
Rarely undergoes malignant degeneration
Radiologic images: various images
Case reports: 68 year old man with cyst and sudden death (Am J Forensic Med Path 2002;23:368), woman with cerebellopontine angle cyst that degenerated into squamous cell carcinoma (Neurosurg 2002;97:1237)
Gross: well defined round mass has irregularly nodular capsule with pearly discoloration
Micro: fibrous wall lined by keratinizing squamous epithelium; contains squames but no skin adnexae and no hair
Micro images: fibrous wall with focal squamous epithelium but no skin adnexae
Cytology images: superficial squamous cells
Positive stains: CK8, CK20
DD: dermoid cyst, cystic craniopharyngioma (CK8-, CK20-)
References: eMedicine
Often in pineal gland
May cause hydrocephalus and sudden death
Case reports: 22 year old man with sudden death due to hydrocephalus from pineal gland cyst (J Clin Path 1996;49:267-free full text), 19 year old woman with thalamic glial cyst causing hydrocephalus due to hemorrhage (Neurol Med Chir (Tokyo) 1997;37:284)
Micro: wall lined by gliosis, Rosenthal fibers present, variable hemosiderin; no epithelial lining
Micro images: pineal gland cyst adjacent to midbrain; pineal tissue (left) and glial tissue (right)
Positive stains: GFAP
Also called diverticulum
Overlying hemispheres or in posterior or lateral epidural space in spinal canal
Radiologic images: various images (figures 1-9)
Micro: lined by fibrous tissue resembling dura, no arachnoid membrane
Micro images: fibrocollagenous layer without arachnoid
References: Neurosurg Focus 2002;13 (spinal extradural meningeal cyst-PDF file, free full text)
Heterogeneous group of lesions with uncertain etiology
Brain and spinal cord, usually older adults
Rarely rupture and cause meningitis; may be associated with seizures or mass effect
Radiologic images: MRI shows large cerebral cyst
Case reports: neuroepithelial cysts of posterior fossa (Can Assoc Radiol J 1996;47:126), causing movement disorders (Can J Neurol Sci 2003;30:393), 4
Treatment: drainage, possibly with placement of drainage device to prevent recurrence
Micro: epithelioid surface with underlying fibrosis or fibrillary glia, but no obvious ventricular or subarachnoid connection
May resemble a cystic tumor
Usually incidental finding present in 2-3% of adults, but may hemorrhage
Large cysts may compress aqueduct
Fine needle aspiration may provide rapid diagnosis (Cancer 2005;105:80)
Radiologic images: various images #1; #2
Gross images: pineal cyst
Micro: resemble glial cyst; dense gliosis with Rosenthal fibers; may be pinker than surrounding pineal gland (with dark calcifications); may compress pineal tissue and make it appear hypercellular; no epithelial or mesenchymal features
Cytology: small, uniform polygonal cells
Micro images: cyst is separated from partially calcified normal pineal tissue by thick layer of gliofibrillary tissue with Rosenthal fibers #1; #2
DD: pilocytic astrocytoma; also (by Xray) - germ cell tumor, enterogenous cyst, epidermoid cyst, dermoid cyst
References: Ann Diagn Path 1997;1:11
Glial cyst in cerebellum
No communication with ventricles
Case reports: 42 year old man (J Neuroradiol 2001;28:209),
Micro: wall lined by gliosis, Rosenthal fibers present, no epithelial lining
Positive stains: GFAP
References: J Neuroradiol 1995;22:48
Defined as a pathological cavity in the brain or spinal cord, especially in syringomyelia
Dissection of white matter of brainstem or spinal cord NOT continuous with ventricle or spinal canal, and not lined by ependymal cells
Usually from spinal cord (in surgical specimens)
Related to trauma, tumors or abnormalities of cranio-cervical junction
Gross images: syrinx in spinal cord
CNS Tumors
13K deaths in US annually (2% of cancer deaths)
Peaks in childhood, then declines to age 25 years, then increases with age
Childhood tumors: 33% in anterior fossa (supratentorial), 67% in posterior fossa (astrocytoma-26%, medulloblastoma/PNET-24%, ependymoma-14%)
Adults: metastases are more common than primary brain tumors but are usually not biopsied; of biopsied tumors, 67% arise in anterior fossa (glioma-33%, meningioma-13%, metastases-12%, pituitary adenoma-5%), 33% in posterior fossa (schwannoma-8%, misc.-33%)
Most common spinal cord tumors are schwannoma, meningioma and ependymoma
Metastasis of primary CNS tumors outside CNS is rare, usually occurs along brain and spinal cord via subarachnoid space or due to surgery related implantation of tumor cells into vessels
Benign appearing tumors may still be infiltrative and difficult to resect
Tumors may arise from neural stem cells, precursors of neurons and glial cells, recently discovered in mature brain
Symptoms: focal deficits, seizures, increased intracranial pressure (due to mass effect, hydrocephalus, cerebral edema), herniation
Intra-axial: within brain and spinal cord
Extra-axial: not within brain and spinal cord (such as meningioma)
Supratentorial: above tentorial membrane - cerebrum
Infratentorial: below tentorial membrane - cerebellum, brainstem or spinal cord
Labeling index/proliferation index: percentage of MIB1+ or PCNA+ nuclei (compared to all nuclei), usually in regions of highest proliferation; useful prognostic indicator (high values associated with poorer prognosis)
Factors to consider:
(1) Neoplasm: yes or no? Yes - hypercellular, composed of atypical fibrillar cells; if no, may be infectious, inflammatory, toxic-metabolic, traumatic, vascular, development or degenerative
(2) Primary or metastatic neoplasm?
(3) Glial, neuronal and other primary tumor considerations
(4) Correlate pathologic diagnosis with age, sex, location and imaging characteristics
Multiple lesions are often metastases, melanoma, medulloblastoma (late) or lymphoma
Differential diagnosis (adopted from Sternberg):
Fibrillar cells: fibrosis, granuloma, astrocytoma, astroblastoma, ependymoma, glioblastoma, gliosarcoma, ganglion cell tumor, central neurocytoma, pineocytoma, polar spongioblastoma, fibroblastic meningioma, MFH, schwannoma, neurofibroma, Langerhans cell histiocytosis, hemangioblastoma, melanoma
Epithelioid cells: xanthogranuloma or gitter cells, oligodendroglioma, choroid plexus tumor, medulloepithelioma, meningioma, chordoma, paraganglioma, pituitary adenoma, endodermal sinus tumor, embryonal carcinoma, hemangioblastoma, craniopharyngioma, metastatic carcinoma, melanoma
Conspicuously different cells: oligoastrocytoma, glioblastoma or gliosarcoma with epithelial metaplasia, ependymoma, ganglion cell tumor, desmoplastic medulloblastoma, transitional meningioma, germinoma, teratoma, choriocarcinoma, desmoplastic carcinoma, melanoma
Extensively revised in 1993 (1993 classification; reference: Brain Pathol 1993;3:255)
Later revised in 2000 (J Neuropathol Exp Neurol 2002;61:215; WHO book is out of print but US National Cancer Institute has summary); WHO classification and ICD-O codes-PDF File
Neuroepithelial tumors: glial, neuronal, mixed glial-neuronal or nonglial
Glial tumors: astrocytic, oligodendroglial, mixed, ependymal, unknown origin
Glial tumors
Includes astrocytoma, ependymoma, glioblastoma, oligodendroglioma and various subtypes / combinations
“Glioma” may be used for frozen section, but is not a final diagnosis
Important to identify oligodendroglial component, due to effectiveness of chemotherapy for these gliomas
Most common CNS tumor
Presence of thrombosed vessels in tumors may predict postoperative systemic thromboses (J Neurosurg 1998;89:200)
Classification of gliomas:
Benign: does not recur; applies to pilocytic astrocytomas, certain gangliogliomas and ependymomas; may still have poor prognosis due to location that makes it difficult to resect completely
Low grade: may recur as high grade and kill patient
Gliomatosis cerebri: diffuse and extensive involvement of CNS associated rarely with gliomas; MRI and biopsy helpful for diagnosis
Micro: biopsies of tumor epicenter have cellularity greater than surrounding brain; biopsies of margin only are difficult to grade; often contain granular calcifications among hypercellular glia; also microcysts and mitotic figures (depending on tumor grade); may have uneven distribution of cellular density that obscures gray-white junction or spawns secondary structures of Scherer (subpial and perineuronal neoplastic glia)
Positive stains: GFAP
Negative stains: collagen, reticulin, fibronectin
Exceptions:
Oligodendroglioma cells have variable GFAP and are Leu7+ and S100+
Xanthoastrocytomas are reticulin+
DD: gliosis (even distribution of cellular density, contracts instead of expanding near hypercellular glia; usually less pleomorphism, no nuclear hyperchromasia, no nuclear cluster formation, no nuclear molding, no mitotic figures, no calcifications)
Often 5-25 years after treatment of pituitary adenoma or craniopharyngioma
In children, often follows treatment for acute lymphoblastic leukemia
Usually anaplastic astrocytoma or glioblastoma
Case reports: 48 year old woman with gliosarcoma arising from irradiated anaplastic ependymoma (Hum Path 2004;35:512), arising 11 years after prophylactic brain radiation and intrathecal methotrexate for ALL at age 3 years (Childs Nerv Syst 1988;4:296)
References: Tumori 1994;80:220
Astrocytic tumors
Most fibrillar of CNS tumors; other fibrillar tumors are tanycytic ependymoma and subependymoma
Low grade astrocytomas resemble gliosis
Affect entire CNS
Usually young adults
Most common primary brain tumor in children
Indicate the grading system used
Brainstem: 20% of primary brain tumors age 20 years and less are astrocytomas; 50% progress to glioblastoma at autopsy
Gross images: mass effect; brainstem glioma #1; #2; infiltrative margin
Micro: hypercellular; nuclei are angular and indent each other; infiltrative margins; often microcystic degeneration (easier to recognize on unfrozen tissue; on frozen section, microcysts contain protein)
Micro images: hypercellular tumor with infiltrative margin (left) vs. normal brain (right)
Positive stains: GFAP (variable)
Not a specific subtype, but a group of entities with similar gross features
Usually low grade unless cysts contain necrotic material
Macroscopic cysts are associated with cerebellar pilocytic astrocytoma
DD: hemangioblastoma
Granular cell astrocytic neoplasms
Rare morphologic variant of astrocytoma and glioblastoma (not a separate WHO designation)
A degenerative change (AJSP 1996;20:55), not a distinct genetic subtype (Brain Path 2003;13:185)
More aggressive than non granular cell tumors, usually fatal (AJSP 2002;26:750)
Case reports: granular cell appearance due to Rosenthal fibers (Acta Neuropathol (Berl) 1993;86:100)
Micro: prominent population of atypical granular cells (large, round with eosinophilic, PAS+ granules, eccentric nuclei), often with transition to a classic infiltrating glioma; often lymphocytic infiltrate or macrophages
Positive stains: PAS (diastase resistant), S100, GFAP, intercellular reticulin; CD68, EMA and ubiquitin are due to lysosomes
EM: cytoplasmic granules are lysosomes, some autophagic
DD: neuroendocrine tumors, histiocytic lesions, demyelinating disease, infarctions
References: Semin Diagn Pathol 1999;16:91 (review), Clin Neuropathol 2000;19:170, Neuropathol Exp Neurol 1986;45:447 (granular cell glioblastoma), Hum Path 1993;24:805 (granular cell anaplastic astrocytoma)
WHO grading of astrocytomas (2000)
1: pilocytic - circumscribed, biphasic, bipolar and multipolar cells, Rosenthal fibers, microcysts, granular bodies; no/rare mitotic figures, no/rare vascular proliferation, no/focal necrosis
2: diffuse - moderately hypercellular, monotonous cells, mild nuclear atypia, no/minimal mitotic activity
3: anaplastic - increased cellularity and diffuse infiltration, increased nuclear atypia, increased mitotic activity
4: glioblastoma - vascular proliferation, necrosis, crowded anaplastic cells, marked nuclear atypia, brisk mitotic activity
Pilocytic means “hair like”, due to long, bipolar processes
Most common CNS neoplasm of childhood; incidence of 1/100K; peak age 8-13 years
Better prognosis than diffuse types, particularly if resectable (such as cerebellar tumors)
May be multicentric
Usually involves midline structures in posterior fossa including cerebellum; also third ventricle, thalamus, hypothalamus, neurohypophysis
10 year survival is 100% if supratentorial and gross total resection vs. 74% if subtotal resection
Invasion of subarachnoid space and endothelial proliferation are not poor prognostic factors
Treatment: resection; radiation and chemotherapy for tumors of optic pathway and hypothalamic region; rarely recurs or disseminates
Gross: microcystic or macrocystic; may have mural nodule
Gross images: cerebellar tumor #1; #2 (arrow at mural nodule); #4; #5 with hemorrhage; optic nerve tumor
Micro: bipolar neoplastic cells with elongated hairlike processes that are arranged in parallel bundles and resemble mats of hair; Rosenthal fibers, often associated with eosinophilic protein droplets (resembling foamy macrophages); may have microscopically infiltrative margin; mural nodule may be highly vascular; often calcifications
Rarely malignant degeneration with hypercellularity, mitotic figures and necrosis
Micro images: bipolar cells with Rosenthal fibers #1; #2; #3; #4; various images #1; #2; various images with case history #1; #2 (with disseminated tumor)
Cytology images: bipolar long astrocytic processes and central Rosenthal fiber
Positive stains: GFAP (strong), PTAH, PAS (protein droplets), alpha-1-antichymotrypsin (protein droplets)
DD: gliosis, hemangioblastoma (cells appear fibrillar on frozen section)
References: Radiographics 2004;24:1693 (review; free full text); Br J Neurosurg 2004;18:613 (adults)
Fibrillary, protoplasmic and gemistrocytic (see below) subtypes are called diffuse, but fibrillary is more common
80% of adult primary brain tumors; usually cerebrum, but can be anywhere in CNS
Age 40+ years
May become more anaplastic over time
Grade of small biopsies may not be representative
Median survival is 6-8 years, but rarely has rapid progression and death
Treatment: surgery; average survival is 7 years with wide variability
Poor prognostic factors: high Ki-67, p53, brainstem location
Radiology: mass effect, peritumoral edema
Gross images: diffusely infiltrative tumor
Micro: fibrillary cells contain cellular fibrillar processes and nuclei with greater angularity and density than normal CNS, also intracytoplasmic fibrils and longer cell processes than protoplasmic astrocytomas; microcysts are particularly prominent in protoplasmic subtype, may degenerate into macrocysts; margin gradually diminishes in cellularity and intermingles with normal CNS; may form secondary structures of Scherer
Micro images: smear shows neoplastic astrocytes with cytoplasmic glial processes and variable nuclear atypia; well differentiated tumor, HAM56 negative (no macrophages)
Positive stains: PTAH (fibrillary subtype), GFAP (fibrillary and protoplasmic subtypes)
DD: gliosis, oligodendroglioma (round nuclei with perinuclear halos, chicken wire vessels, mineralization, GFAP negative)
Protoplasmic astrocytoma-grade II
Rare; 3-4% of supratentorial brain tumors
Variant of diffuse astrocytoma; WHO considers a variant of grade II astrocytoma
Mean age 21 years, often with long history of seizures before diagnosis, male predominance
Often in temporal and frontal lobes
Thought to derive from process-poor protoplasmic astrocytomas
Generally a benign clinical course after resection
Micro: proliferation of glial cells with few cytoplasmic processes; round/oval nuclei, microcystic background, no/rare mitotic figures; no vascular proliferative changes, no necrosis
Micro images: scant or vacuolated cytoplasm with short processes, vesicular nuclei and prominent nucleoli #1; #2; GFAP+
Positive stains: GFAP (focal/weak or negative)
Negative stains: Ki-67 (<1% staining)
Molecular: no 1p-
DD: microcystic oligodendroglioma (1p-), dysembryoplastic neuroepithelial tumor (associated with cortical dysplasia, usually multifocal or multinodular)
References: Hum Path 2004;35:317, Am J Clin Path 1995;103:705
Gemistocytic astrocytoma-grade II
Variant of diffuse astrocytoma
May be more aggressive than other grade II astrocytomas (J Neurooncol 2005 [Epub ahead of print], J Neurosurg 1991;74:399)
Restrict diagnosis to cases with at least 20% gemistocytic cells
Case history: congenital brain tumor with various images
Gross images: frontal lobe tumor
Micro: conspicuous (20% of more) gemistocytes (plump cells with abundant, hyaline pink cytoplasm and no/minimal blue Nissl substance, hyperchromatic and angular nuclei at border of cell), perivascular lymphocytic cuffs; infiltrative margins; no neoplastic neurons