HISTOPATH: Neuro-oncology Flashcards
How common are CNS tumours in children vs adults?
In adults make up 1-2% of all tumours
In children are the most common tumour type making up ~25% of all tumours
What is the histological classification for CNS tumours (based on cell of origin)?
Extra-axial:
- Meningothelial cells – meningioma
- Schwann cells – schwannoma
Intra-axial:
- Astrocytes – astrocytoma
- Oligodendrocytes – oligodendroglioma
- Ependyma – ependymoma
- Neurons – neurocytoma
-
Embryonal cells – medulloblastoma
- Children
What is the aetiology of CNS tumours?
- Radiation to head and neck: meningiomas, rarely gliomas N.B. mobile phone use does not increase risk
- Neurocarcinogens
-
Genetic predisposition (<5% of primary brain tumours)
- Neurofibromatosis is most common form
- Autosomal dominant inheritance
What are the signs and symptoms of CNS tumours, in general and based on location?
Often non-specific and subtly growing (can have a short history in aggressive lesions):
- Intracranial HTN –> headache, vomiting, changed mental state
- Supratentorial –> focal neurological deficits, seizures, personality change
- Subtentorial –> cerebellar ataxia, long tract signs, cranial nerve palsies
What are the neuroimaging studies used in CNS tumours?
- CT scan / PET-CT (tracer compounds for hotspots)
- MRI scan (multiple types) = MR-spectroscopy (metabolism), perfusion MRI, f-MRI
What are 5 purposes of imaging in CNS tumours?
- Assess tumour type
- Guide resection and biopsy
- Assess post-surgery
- Assess response to treatment
- Follow-up recurrence
- Progression
What are the management options for CNS tumours?
-
Surgery (maximal safe resection aims to obtain and extensive excision with minimal damage to the patient)
- Resectability is dependent on the location, site and number of lesions
- Craniotomy = debulking (subtotal and complete resections)
- Open biopsies = inoperable but approachable tumours
- Stereotactic biopsy = open biopsy not indicated
-
Radiotherapy
- Used for… low and high-grade gliomas, metastases
-
Chemotherapy
- Used for… high-grade gliomas (temozolomide)
- Biological agents (EGFR inhibitors, PD-1 inhibitors etc.)
What categories does the WHO classification system for CNS tumours use?
- Tumour type (cell of origin) = histological type, predicts behaviour (i.e. rate of spread)
-
Tumour grade (differentiation) - histological criteria (e.g. proliferative activity, cell differentiation, necrosis)
- Grade I = benign, long-term survival - LOW grade, LONG survival - predicts survival
- Grade II = cause death in >5 years - LOW grade, LONG survival
- Grade III = cause death <5 years - HIGH grade, SHORT survival
- Grade IV = cause death <1-year - HIGH grade, SHORT survival
IS staging used in WHO classification of CNS tumours?
No staging because typically no spread
What are 3 purposes of grading of CNS tumours?
- Stratifies tumours by their OUTCOMES (it is rarely based on their genetic profile)
- Grading is based on a tumour’s NATURAL HISTORY and does not consider the response to treatment, it GUIDES treatment
- Grading tells us… SURVIVAL
Grading does not tell us… therapy response, disease spread, cell of origin
Does grading of CNS tumours tell us about:
- Therapy response
- Disease spread
- Cell of origin
No for all
Which type of CNS tumour is the only one that is staged?
Medulloblastoma
Name 6 types of glial cells.
- Astrocytes
- Oligodendrocytes
- Ependymal cells
- Schwann cells
- Microglia
- Satellite cells
What is the most common primary type of CNS tumour?
Glial tumour
What are the types of glial tumours?
- Circumscribed gliomas
- Diffuse gliomas
What are the grades of circumscribed gliomas? Who is most affected? Does it transform?
Grade I-II
Children
Rare malignant transformation may occur
What are the types of circumscribed gliomas?
- Pilocytic astrocytoma (grade I) - most common
- Pleomorphic xanthoastrocytoma (grade II)
- Subependymal giant cell astrocytoma (grade I)
What genetics may be implicated in circumscribed gliomas?
BRAF mutation present in 50% of cases (MAPK pathway mutation)
What is the most common child brain tumour? What is its grade?
Pilocytic astrocytoma (WHO grade I)
What are these histological features present in pilocytic astrocytoma?
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Histopathology:
- Piloid (hairy) cell
- Rosenthal fibres and granular bodies
- Slowly growing with low mititic activity
What are the features of pilocytic astrocytoma on MRI?
- Cerebellar
- Well circumscribed
- Cystic
- Enhancing
What % of pilocytic astrocytomas are associated with BRAF mutation?
70% of cases
Name 2 types of diffuse gliomas.
- Diffuse astrocytoma (grades II-IV)
- Oligodendroglioma (grades II-III)
What are the general features of diffuse gliomas? (location, grades, age, malignancy) What genetic mutation are they associated with?
- Grades II or higher
- Adults
- Supratentorial
- Malignant progression
- IDH1/2 mutation present in 30% of cases (positive prognostic factor)
In diffuse glioma, what is the importance of IDH1/2 mutation for prognosis?
It is a positive prognostic factor
What are the typical grades of diffuse astrocytoma? What age groups are affected ? Where does it usually occur in the brain?
WHO grade II-V
Patients 20-40yo
Cerebral hemispheres (adults), cerebellum (children)
What is seen on MRI/MR spectroscopy in diffuse astrocytoma?
MRI:
- T1 hypointense,
- T2 hyperintense,
- non-enhancing lesion
Low choline: creatinine ratio at MR-spectroscopy
What is the complication of astrocytomas if left untreated over several years?
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An astrocytoma (grade II-III) eventually will become a glioblastoma (grade IV) over several years
What are the histological features of diffuse astrocytoma?
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- Low to moderate cellularity
- Mitotic activity negligible/absent
- Vascular proliferation and necrosis absent
Who is most affected by glioblastoma multiforme (GBM)? What is the grade?
Most patients >50yrs
WHO grade IV
What is seen on histology in GBM? What is seen in cytology on GBM?
MRI:
- heterogenous enhancing post-contrast
Cytology:
- high cellularity,
- high mitotic activity,
- microvascular proliferation (neoangiogenesis),
- necrosis
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Metastatic deposit
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Pilocytic astrocytoma, WHO grade I
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Survival
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IDH1/2
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Metastatic
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Glioblastoma - option 1
- Meningioma (WHO I)
- Medulloblastoma (WHO grade 4)
- Glioblastoma (WHO grade 4)
- Pilocytc astrocytoma (WHO grade I)
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Pilocytic astrocytoma (WHO grade I) - common in chilren and usually in cerebellum
Is a genetic mutation a common cause for GBM?
90% occur de novo with wildtype IDH
10% occur secondary to astrocytoma (progression) and have the IDH mutation (positive prognostic factor)
What is the grade of oligodendrogliomas? When do they usually occur?
WHO grade II-III
Patients 20-40yrs
Compared to astrocytomas, what is the prognosis with oligodendrogliomas? Why?
Better prognosis than astrocytomas
- Slow growth –> amenable to resection
- Better chemo- and radio-therapy response
Which CNS tumour cytology is this? Why is it called fried eggs appearance?
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Cytology: round cells with clear cytoplasm (“fried eggs”)
What is seen on MRI in oligodendroglioma?
MRI: no/patchy contrast enhancement
MRI/MRSpec not predictive of transformation
What % of oligodendrogliomas are associated with IDH1/2 mutations? What other mutation occurs?
IDH1/2 mutation and co-deletion of 1p/19q present in ~100% of cases
Positive prognostic factor
What is the 2nd most common CNS tumour?
Meningiomas
Usually occurs in adults >40yrs
How do meningiomas appear on MRI?
- Extra-axial,
- Isodense,
- Contrast-enhancing
What does HPF stand for?
High power field
What are the mitotic activities of grade I-III meningiomas?
- I - <4 mitotic activity per 10 HPF
- II - 4-20 mitotic activity per 10 HPF
- III - >20 mitotic activity per HPF
What grade are most meningiomas?
- 80% grade I
- 20% grade II
- 1% grade III
What is the histopathology of meningiomas?
- Attaches to meninges but does not typically invade, just displaces brain matter
- If they do invade, it is often a micro-invasion (as pictured)
- Globules found on histopathology
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What is the most frequent cause of CNS tumours in adults?
CNS metastasis
What are the features of CNS metastases?
- Increasing in frequency due to longer survival
- Often multiple
- Origin may be difficult to determine and may be the first presentation of disease
What are the most common origins of CNS metastases?(3)
- Lung
- Breast
- Melanoma
What is the prognosis of CNS metastases?
Very poor
What is this type of CNS tumour growth called?
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Pseudoinvasion along the Virchows-Robin space
Where do CNS metastases usually grow and why?
Grey-white junction
- Structure of cerebral blood vessels change here + become smaller as they enter the white matter
- Therefore, neoplastic emboli tend to get stuck at this level and then start growing
What grade are medulloblastomas?
Grade IV
What is the cell origin of medulloblastoma? Where does it grow?
Embryonal origin - from the neuroepithelial precursors of the cerebellum/dorsal brainstem
Grows in the cerebellum
Who is most affected by medulloblastomas?
Children - it is the 2nd most common brain tumour in children
Outcomes improved with radio-chemotherapy
What is the histology of medulloblastomas?
- “Small blue round cell” tumour (i.e. it is a blastoma* / of a primitive cell line)
- Expression of neuronal markers (very little differentiation) – i.e. synaptophysin
- Homer-Wright rosettes are a feature of primitive neuronal differentiation
Another blastoma is Wilm’s tumour.
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What type of tumour has this histology? What is the name given to this appearance?
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Homer-Wright rosettes
Medulloblastoma
What are the 4 groups of medulloblastomas?
- WNT-activated medulloblastoma
- SHH-activated “”
- Group 3 “”
- Group 4 “”
- Seizure following 2 weeks of left arm and leg weakness
- MRI showing heterogeneous enhancing right frontal lesion, started on steroids
- Partial response to steroids with improved dexterity of the left arm and leg
- A tumour was partially resected
Answers:
- Glioblastoma (WHO grade IV)
- Oligodendroglioma (WHO grade II)
- Metastatic carcinoma
- Diffuse astrocytoma (WHO grade II)
- 5-year-old boy
- Had headache and vomiting in the morning for 2 weeks
- Symptoms worsened and the vision became blurred
- Fundoscopic exam: papilledema
- MRI showing cystic cerebellar lesion à tumour was removed
Answers:
- Glioblastoma (WHO grade IV)
- Medulloblastoma (WHO grade IV)
- Oligodendroglioma (WHO grade II)
- Pilocytic astrocytoma (WHO grade I)
- 45-year-old female
- History: pulmonary lobectomy
- 2 days of headache and vomiting
- Worsening headache
- CT: right frontoparietal SOL with minimal midline shift to the left
- DDx: primary tumour, metastasis, abscess
Answers:
- Glioblastoma (WHO grade IV)
- Astrocytoma (WHO grade II)
- Metastatic carcinoma
- Oligodendroglioma (WHO grade II)