Histo: Neuro-Oncology Pt.2

Question 1

List some examples of circumscribe gliomas.

Answer 1

• Pilocytic astrocytoma (MOST COMMON)
• Ependymoma
• Subependymal giant cell astrocytoma

Question 2

List some key features of pilocytic astrocytomas (WHO grade 1)

Answer 2

• Mainly occurs in children (1st and 2nd decade of life)
• Associated with NF1
• Often located cerebellar, optic hypothalamus, or brainstem
• BRAF mutation in 70% of cases

Question 3

What is the hallmark histological feature of pilocytic astrocytoma?

Answer 3

• Piloid (hairy) cell
• Often see Rosenthal fibres and granular bodies
• Slow-growing with low mitotic activity

Question 4

List some key features of astrocytoma (WHO grade 2, 3, and 4)

Answer 4

• Usually affects adults 20-40 years old
• Cerebral hemispheres are the most common site in adults
• Can progress to become a higher grade (malignant progression)
• IDH1/2 mutation in 80% of cases

Question 5

Describe the histology of astrocytoma (WHO grade 2, 3, and 4)

Answer 5

• Low cellularity and mitotic activity
• No vascular proliferation or necrosis
• IDH mutants can be detected with immunocytochemistry

Question 6

What can astrocytomas eventually become?

Answer 6

Glioblastoma (after 5-7 years)
Grade IV astrocytoma

Question 7

What is the most aggressive form of astrocytoma

Answer 7

Glioblastoma multiforme (WHO stage 4)

Question 8

List some key features of glioblastoma multiforme.

Answer 8

• Grade IV
• Most patients > 50 years
• Affects cerebral hemispheres
• most freq glioma
• median survival 8months

Question 9

Describe the histology of GBM

Answer 9

• High cellularity and high mitotic activity
• Neoangiogeneis
• Necrosis

Question 10

What does glioblastoma multiforme tend to arise from?

Answer 10

90% arise de novo and have wildtype IDH

10% occur secondary to astrocytoma and have IDH mutation

Question 11

What is the second most common primary intracranial tumour after gliomas?

Answer 11

Meningioma

Question 12

List some key features of meningioma.

Answer 12

• Mainly low grade (I and II)
• Rare in patients <40, incidence increases with age
• Can be multiple (e.g. in NF2)

80% - grade 1 (benign)
20% - grade 2 (atypical)
1% - grade 3 (malignant)

Question 13

What cell type does meningioma originate from

Answer 13

Meningioepithelial cells of arachnoid mater

Question 14

Which histological feature of meningioma is important in determining grade?

Answer 14

Mitotic activity (number of mitoses per 10 high power fields)

• Grade 1: < 4
• Grade 2: 4-20
• Grade 3: > 20

NOTE: brain invasion is also an important thing to assess (presence of brain invasion makes it grade II)

Question 15

How does grade of meningioma affect the management options?

Answer 15

Grade II and III requires radiotherapy as well as surgery

Question 16

What is a medulloblastoma?

Answer 16

• Embryonal tumour originating from neuroepithelial precursors of the cerebellum and dorsal brainstem
• They are always found in the cerebellum

Question 17

Describe the histological appearnce of medulloblastoma.

Answer 17

Small blue round cell tumour with expression of neuronal markers (very little differentiation)

NOTE: snaptophysin is an example of a neuronal marker

Question 18

Describe the role of methylome profiling

Answer 18

• Most tumours have characteristic DNA methylation patterns of CpG islands
• This methylation signatures is stable and can be used to identify the tumour cell origin

Question 19

Which tumours most commonly metastasise to the brain?

Answer 19

• Lung
• Breast
• Melanoma
• Renal cell

Question 20

How can the origin of brain metastases be identified

Answer 20

Immunohistochemistry

Question 21

Where in the brain do metastases tend to be found?

Answer 21

• At the grey-white junction
• This is because the cerebral blood vessels become smaller as they enter the white matter so neoplastic emboli get caught here

Question 22

What mutation is associated with a better prognosis?

Answer 22

IDH mutation

found in IDH mutant diffuse gliomas

Question 23

Useful predictor of recurrence in meningiomas?

Answer 23

Tumour grade

based on:

• histology
• molecular markers