Chapter 26 - Brain Flashcards
What are the three most useful pieces of information in diagnosing brain lesions?
The patient’s age
The location of the lesion
The radiographic appearance of the lesion
How does a demyelinating lesion appear on histology?
Abundant foamy macrophages and an abscence of obvious tumor cells
What lesions can arise from the following normal brain cells?
- Astrocytes
- Oligodendroglia
- Ependyma
- Neurons
- Meninges
- Astrocytoma
- Oligodendroglioma
- Ependymoma
- Neurocytoma, gangliocytoma
- Meningioma, hemangiopericytoma
What lesions can arise from the following brain cells?
- Choroid plexus
- Pituitary
- Schwann cells
- Stromal/vascular cells
- Choroid plexus papilloma / carcinoma
- Pituitary adenoma
- Schwannoma
- Hemangioblastoma
What lesions can arise from the following brain cells?
- Embryonal (immature) cells
- Pharynx remnants
- Germ cell remnants
- Notochord remnants
- Medulloblastoma, PNET, neuroblastoma
- Craniopharyngioma, Rathke cleft cyst
- Germinoma, teratoma
- Chordoma
How are CNS tumors graded and staged?
There is no “benign” & “malignant”, and there is no TNM staging.
WHO grades I-IV; I-II is “low grade”, while III-IV is “high-grade”.
Grading features are the usual.
How should intraoperative specimens be evaluated? Why?
In addition to freezing, should also be smeared and/or touch-prepped.
Highlights fibrillary processes and preserves nuclear detail. Also indicates cohesiveness of the tumor.
What CNS tumors are noncohesive?
Lymphoma, pituitary adenoma, oligodendroglioma
How are astrocytes divided?
Into diffuse (infiltrating) and circumscribed variants (basically just pilocytic astrocytoma).
Diffuse: Well-differentiated (II), anaplastic (III), and glioblastoma (IV).
What features define grades III and IV astrocytomas?
III: Hypercellularity & mitoses
IV: Microvascular proliferation or necrosis (especially pseudopalisading)
Describe the general morphology of an astrocytoma.
The tumor cells generally resemble normal cells with no visible architecture or cell borders. Recognize the presence of too many nuclei that are hyperchromatic, large, & irregularly shaped.
Describe the clinical significance of pilocytic astrocytoma.
A circumscribed and indolent form of astrocytoma occuring in young patients, usually in association with the cerebellum, optic nerve, hypothalamus, or ventricles.
Describe the morphology of pilocytic astrocytoma.
Matted hair-like background. Rosenthal fibers and eosinophilic granular bodies.
Name and describe two well-circumscribed astrocytomas besides pilocytic.
Pleomorphic xanthoastrocytoma: Seizure-causing tumor of young adults found in the cerebral cortex
Subependymal giant cell astrocytoma: Seen in tuberous sclerosis
What is gliosis and how does it appear?
How can it be distinguished from gliomas?
A reactive process with shortening of astrocytes and taking on a stellate shape.
Gliomas are more likely to be microcystic, calcified, and show mitoses & satellitosis (clustering around neurons/vessels).
Where are oligodendrogliomas usually located?
What grade are they?
Usually in the frontal / temporal lobes of adults
Usually grade II, but vascularity & necrosis will push it to grade III.
Describe the morphology of oligodendroglioma.
Small round nuclei surrounded by clear halos. Chromatin is like a plasma cell. Exhibits satellitosis. Can be net-like or microcystic & calcifying.
What feature is most important to identifying oligodendroglioma?
Deletion of 1p and/or 19q.
Where are meningiomas located?
How are they graded?
Always dural-based.
Usually grade I, but can be II (atypical) or III (malignant) with signature histologic patterns.
Describe the morphology of meningioma.
Extremely unpredictable, with 16+ subtypes. Distinguished by meningothelial cells. Look for whorls and psammoma bodies.
Describe the appearance of meningothelial cells.
Invisible cell borders, syncytial. Regular small and streaming nuclei.
Describe the following subtypes of meningioma:
Clear cell
Chordoid
Clear cell: Grade II. Glycogen-filled, so clear in appearance.
Chordoid: Grade II. Resembles chordoma, with myxoid background and cords of cells.
Describe the following subtypes of meningiomas:
Rhabdoid
Papillary
Rhabdoid: Grade III. Plump pink cells with discrete cell borders, similar to rhabdomyosarcoma
Papillary: Grade III. Syncytial meningothelial cells on fibrovascular cores.
How can a given histologic type of meningioma be “up-graded”?
Cytologic criteria (cellularity, pleomorphism, >4/10hpf mitoses, necrosis)
Brain invasion
What are hemangiopericytoma and solitary fibrous tumor?
Tumors that probably arise from hemangiopericytes that are dural-based and well-circumscribed.
Hemangiopericytoma is more aggressive: Blue & cellular with staghorn vessels. More nuclear than meningiomas…
What tumors are usually seen infratentorially?
What are some considerations for frozen here?
Usually tumors of children: Medulloblastoma, pilocytic astrocytoma, ependymoma. Also acoustic neuromas and hemangioblastomas.
The above lesions are easy to distinguish. Note that normal granule cells look like tumor on smear.
What is an acoustic neuroma?
A schwannoma arising from the eighth cranial nerve.
Describe the appearance and significance of hemangioblastoma.
An infratentorial tumor seen in VHL syndrome which resembles CCRCC. Stain for oil red O.
Describe the morphology of schwannoma.
A benign fibrillary tumor with elongated nuclei of alternating low (antoni A) and high (antoni B) cellularity. Makes palisaded arrays (Verocay bodies)
What tumors arise in the midline?
Germinoma
Craniopharyngioma
Chordomas
(embryonic remnants)
Pineal and pituitary tumors
Describe the appearance of craniopharyngioma.
Which occur in adults?
“Adamantinomatous” appearance (looks like developing tooth). Nests of cells boudned by dark palisaded cells, with central areas of stellate cells in a myxoid stroma.
Adults get the papillary type (resembles squamous papilloma)
Describe the morphology of chordomas.
Bluish, mucinous background like IV discs. Physaliphorous tumor cells full of bubbles and growing in cords.
Describe the morphology of pituitary adenoma.
Monotonous cells lacking the normal cellular heterogeneity seen in the pituitary. Looks neuroendocrine.
Describe the morphology of pineocytoma.
Looks like normal pineal gland…
What are ependymomas and how are they graded?
Usually low-grade (II) lesion of young patients. Can be anaplastic (III).
Subependymomas are lower grade (I).
Describe the morphology of ependymoma.
What is a myxopapillary ependymoma?
Circumscribed lesion of cells with pale oval nuclei aligned around blood vessels in pseudorosettes.
Myxopapillary: Occurs in filum terminale, with myxoid background and papillary structure.
What is subependymal giant cell astrocytoma?
A tumor of tuberous sclerosis occurring at the lateral ventricles with very large cell ganglionic appearance.
What is central neurocytoma?
A low-grade lesion of neural origin, usually involving the third ventricle.
Describe the morphology of choroid plexus papilloma / carcinoma.
Papilloma: Bland columnar cells forming pseudostratified layers on large arborizing fronds.
Carcinoma: More solid and mitotically active. Invasive.
Describe the morphology of medulloblastoma.
Sheets of small blue cells. Nuclei resemble small cell carcinoma but can be wedge shaped and in rosettes. Background is fibrillary. Can see differentiated neurons & glia.
What do ependymoblastoma, medullomyoblastoma, retinoblastoma, pineoblastoma, neuroblastoma, and medulloblastoma have in common?
All have rosette morphology. All are grade IV.
Astrocytoma, grade II.
Arrows: Irregular and coarse nuclei
Arrowhead: Fibrillary background
Glioblastoma multiforme
Arrow: Necrosis
Arrowheads: Microvascular proliferation
Inset: Malignant astrocytes with irregular mitoses
Pilocytic astrocytoma
- Fibrillary or hair-like background
- Scattered large dark nuclei
- Rosenthal fibers
- Eosinophilic granular bodies
Reactive astrocytes
Arrow: Dense pink cytoplasm with stubby processes
Oligodendroglioma. Note fried-egg cells suspended in a network of fine capillaries (arrow)
Syncytial meningioma
Arrow: Whorls
Arrowheads: Syncytial groups without cell borders
Left: Clear cell meningioma. Clear glycogenated cells (arrow).
Right: Rhabdoid meningioma. Plump eosinophilic cells (arrow) resembling skeletal muscle.
Hemangiopericytoma
Note staghorn vessel in background of small blue cells between epithelioid and spindled in appearance.
Hemangioblastoma
Note clear lipidized cells with bland nuclei in background of dilated capillaries.
Schwannoma
A: Antoni A area
B: Antoni B area
Arrow: Verocay bodies
Craniopharyngioma, adamantinomatous type.
- Stellate reticulum
- Calcification
- Peripheral palisading
- “wet” keratin
Left: Pituitary adenoma. Note monotonous cells. Reticulin negative.
Right: Normal pituitary. Note heterogeneity. Reticulin shows nesting.
Ependymoma
Arrow: Fibrillary background lining up around vessels. Pseudorosette!
Myxopapillary ependymoma
Arrow: Papillary fibrovascular core surrounded by myxoid stroma and ependymal cells.
Medulloblastoma
Small round blue cells with mitoses (arrow) and apoptoses (arrowhead).
