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?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/385/830/232/q_image_thumb.png?1643196892)
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)