CNS Neoplasm

Question 1

Pilocytic Astrocytoma - Characteristics

Answer 1

Most common CNS neoplasm of childhood

Well circumscribed, non-infiltrative WHO Grade I tumor; often found in the cerebellar hemispheres, optic nerve, and hypothalamus; usually doesn’t undergo malignant transformation and can be treated by surgical resection

Question 2

Pilocytic Astrocytoma - Histopathology

Answer 2

Neoplastic cells with elongated, hairlike processes arranged in parallel bundles; associated with Rosenthal fibers and some cystic areas containing mucin

Question 3

Pilocytic Astrocytoma - Genetics

Answer 3

May show a BRAF:KIAA fusion; BRAF is a protein kinase that plays a key role in cell survival/differentiation/apoptosis pathways

Never possesses IDH1/2 mutation

Question 4

Diffuse Astrocytoma - Characteristics

Answer 4

WHO Grade II tumor with median age of onset 30-40s; usually affects cerebral hemispheres diffusely but does not metastasize outside of CNS

NOT surgically resectable; treated with radiation

Question 5

Diffuse Astrocytoma - Histopathology

Answer 5

Diffusely infiltrative with ill-defined borders; no microvascular proliferation or necrosis

Question 6

Anaplastic Astrocytoma - Characteristics

Answer 6

WHO Grade III Tumor with mean age of onset 45 years; usually affects cerebral hemispheres

Question 7

Anaplastic Astrocytoma - Histopathology

Answer 7

Higher cellularity, increased nuclear pleomorphism, and mitoses compared to WHO Grade II Diffuse Astrocytoma; no necrosis or microvascular proliferation

Question 8

Diffuse Astrocytoma - Genetics

Answer 8

IDH Mutation + TP53 mutation/17P loss

Question 9

Oligodendroglioma - Characteristics

Answer 9

5-15% of all gliomas; can be WHO Grade II or III with mean age of onset ~40 years

Usually arises in cerebral white matter

Often presents as seizures

Not curable by resection - better prognosis than diffuse astrocytoma

Question 10

Oligodendroglioma - Histopathology

Answer 10

Low to moderate cellularity with occasional mitoses; cells have round, monotonous nuclei containing little or no cytoplasm with a “fried egg” appearance

Question 11

Anaplastic Astrocytoma - Genetics

Answer 11

IDH mutation + TP53 mutation/17p loss + 9p loss

Genetic progression of diffuse astrocytoma

Question 12

Anaplastic oligodendroglioma - histopathology

Answer 12

Same as oligodendroglioma WHO Grade II (round, monotonous nuclei with scant cytoplasm and “fried egg” appearance) with increased cellularity, nuclear atypia, mitoses, with occasional vascular proliferation OR necrosis

Question 13

Oligodendroglioma - Genetics

Answer 13

IDH Mutation + 1p/19q co-deletion

Question 14

Anaplastic oligodendroglioma - Genetics

Answer 14

IDH Mutation + 1p/19q co-deletion + 9p/10q loss

Genetic progression of WHO Grade II oligodendroglioma

Question 15

Glioblastoma - Characteristics

Answer 15

WHO Grade IV, accounting for 15% of all intracranial neoplasms; 90% arise sporadically (primary GBM) and 10% occur as a result of progression from lower grade astrocytomas (secondary GBM)

Question 16

Glioblastoma - Histopathology

Answer 16

4 diagnostic criteria:

1. Nuclear abnormalities (atypia, hyperchromatism, variation in size/shape)
2. Mitotic activity
3. Microvascular proliferation
4. Necrosis

Question 17

Primary vs. Secondary GBM

Answer 17

Age of onset - Older for primary GBM (55 years) vs. secondary GBM (45 years)

Duration of symptoms - shorter for primary GBM (<3 months) vs. secondary GBM

Question 18

Ependymoma - Characteristics

Answer 18

Most present in the first 2 decades of life in the 4th ventricle, causing obstructive hydrocephalus; in adults, more likely to occur in the spinal cord

Question 19

Ependymoma - Histopathology

Answer 19

Formation of perivascular pseudorosettes, a perpendicular arrangement of cells around blood vessels with the formation of elongated cell processes

Question 20

Choroid Plexus Papilloma - Characteristics

Answer 20

Neoplastic proliferation of choroid papillary formations occurring more frequently in the lateral ventricles in adults and in the IVth ventricle in children, often producing obstructive hydrocephalus

WHO Grade I, usually curable by surgical resection

Question 21

Medulloblastoma - Characteristics

Answer 21

Most common malignant brain tumor in children; peak incidence 3-8 years

WHO Grade IV with a tendency to spread throughout the CSF

Question 22

Medulloblastoma - Histopathology

Answer 22

Arises from the granule progenitor cells of the external granule layer; proliferation of patternless sheets of embryonal cells with scant cytoplasm, presence of Homer Wright rosettes (circular rings of nuclei with a central, anuclear area filled with cell processes)

Question 23

Medulloblastoma - clinical presentation

Answer 23

Increased ICP signs due to obstructive hydrocephalus of the IVth ventricle: headache, vomiting, papilledema, gait disturbances, nystagmus

Question 24

Meningioma - Characteristics

Answer 24

Most common intracranial neoplasm, peak incidence is women in their 50-60s; usually WHO Grade I but can progress to more advanced grades through accumulation of mutations

Usually solitary; complications include: penetration of the dura, occlusion of venous sinuses, invasion of bone, hyperostosis

Question 25

Schwannoma - Characteristics

Answer 25

Slow growing tumors found on cranial nerves 3-12 and spinal nerve roots; malignant transformation is rare

Question 26

Acoustic Neuroma

Answer 26

i.e. Vestibular (CN VIII) Schwannoma Bilateral vestibular schwannoma is characteristic of Neurofibromatosis Type II

Question 27

Familial Tumor Syndromes

Answer 27

``` Neurofibromatosis - Types I and II Tuberous Sclerosis Von Hippel Lindau Disease Cowden Disease Turcot's Syndrome ```

Question 28

Which systemic tumors most commonly metastasize to the brain?

Answer 28

``` Breast Lung Kidney Melanoma GI tract ``` *Solid neoplasms of childhood rarely metastasize to the brain