CNS Tumors

Question 1

What are a few differences in appearance between astrocytoma and ependymoma in the spinal cord?

Answer 1

Compared to astrocytoma, an ependymoma of the spinal cord has a classic apical cap of blood and is often cystic in appearance. Additionally, ependymomas are more likely central in the cord, are more likely to be associated with a syrinx, and are more common in adults.

Question 2

All high-grade parenchymal brain tumors enhance. What low grade tumors of the brain also enhance?

Answer 2

Ganglioglioma and pilocytic astrocytoma are notable that they are low-grade tumors that may enhance despite being low grade.

Question 3

What is the classic imaging appearance of a pilocytic astrocytoma?

Answer 3

A cystic mass with an enhancing mural nodule.

Question 4

What lesions are classic for crossing the midline of the brain?

Answer 4

Glioblastoma, lymphoma, multiple sclerosis, radiation necrosis and meningioma of the falx.

Question 5

If you see bony reaction/thickening adjacent to a mass what is the significance of this?

Answer 5

Typically, bony reaction surrounding a mass denotes that the mass is extra-axial.

Question 6

What are two masses that are not extra-axial that can nonetheless cause local bony reaction?

Answer 6

DNET and ganglioglioma are two notable exceptions to the aforementioned rule.

Question 7

What are other signs besides bony reaction on imaging that denote a mass is in an extra-axial location?

Answer 7

CSF cleft around mass, displaced subarachnoid vessels, expanded subarachnoid space, broad based dural lesion with tail, able to identify gray matter between the mass on one side and white matter on the other side.

Question 8

What are common cortically based tumors of the brain?

Answer 8

Mnemonic is DOG.

D-dysembryoplastic neuroepithelial tumor.

O-oligodendroglioma.

G-ganglioglioma.

Note that cortical tumors and cortical metastases may be occult on a non-contrast CT or MRI and may have very little surrounding edema.

Question 9

What are some brain tumors that classically may be multifocal on imaging?

Answer 9

Metastases. Primary tumors include lymphoma, GBM, gliomatosis cerebri. Note that gliomatosis cerebri is often low grade and may therefore not enhance but may look as indistinct margins “blurring” between the gray and white matter on CT imaging. Note also that some tumors may seed in a multifocal manner and these include medulloblastoma, ependymoma, GBM and oligodendroglioma.

Question 10

What is SATCHMOE?

Answer 10

This is a mnemonic for sellar and parasellar mass lesions.

S is sarcoid.

A is aneurysm/adenoma/rAthke’s cleft cyst.

T is teratoma.

C is craniopharyngioma.

H is hamartoma, hypophysitis, histiocytosis (LCH) and hypothalamic glioma.

M is meningioma.

O is optic nerve glioma.

E is eosinophilic granuloma.

Question 11

What are the top differential considerations for lesions that show restricted diffusion on DWI sequences for the following locations: supratentorial, CP angle, temporal horn, pediatric posterior fossa?

Answer 11

Supratentorial: lymphoma or abscess

CP angle: epidermoid cyst

Temporal horn: HSV encephalitis

Pediatric posterior fossa: medulloblastoma.

Question 12

What are the most common primary brain tumors that calcify?

Answer 12

Oligodendroglioma is most classic for a calcified brain primary malignancy. However, astrocytomas can calcify and because they are more prevalent, you will see more calcified astrocytomas in real practice although most classic is still the oligodendroglioma in terms of calcified primary brain tumors.

Question 13

What brain tumors are classically bright on T1-weighted images?

Answer 13

Melanoma, hemorrhagic metastases (melanoma, renal cell carcinoma, carcinoid, thyroid carcinoma, and choriocarcinoma), dermoid cyst, cholesterol in colloid cyst.

Question 14

What are classic imaging features for Turcot syndrome?

Answer 14

Glioblastoma, medulloblastoma, and GI polyps.

Question 15

What should you think of if you see an intensely enhancing homogenous solid mass with restricted diffusion in a periventricular location in a patient who is immunocompromised from AIDS or posttransplant state? What about in terms of NUCS studies?

Answer 15

Primary CNS lymphoma vs toxoplasmosis. Remember CNS lymphoma is hot on a nuclear medicine thallium scan whereas CNS toxoplasmosis is not. Both can show uptake with FDG PET/CT.

Question 16

An infratentorial cystic lesion with enhancing mural nodule is most classic for what entity in an adult and what entity in a child?

Answer 16

Adult: hemangioblastoma (think VHL, especially if multiple)

Child: pilocytic astrocytoma.

Question 17

Intraventricular tumors in adults classically include what entities?

Answer 17

Subependymoma, central neurocytoma, xanthogranuloma, colloid cyst and meningioma, others perhaps less classic than these entities.

SMCKNS mnemonic from prior cards . . .

Question 18

If you see a non-enhancing intraventricular mass this should make you first think of what entity?

Answer 18

Subependymoma: circumscribed non-enhancing mass at foramen of monro and 4th ventricle. Lack of enhancement is notable for this entity.

Question 19

What is the top intraventricular mass in the 20-40-year-old population?

Answer 19

Central neurocytoma: #1 intraventricular mass in 20-40-year-olds. These can have a swiss cheese (multiple cystic spaces) appearance and may have robust calcification, often arising from the intraventricular septum.

Question 20

If you see a mass with restricted diffusion arising from the choroid plexus this should make you think of what entity?

Answer 20

Xanthogranuloma—a benign and typically incidental mass of the choroid plexus.

Question 21

What intraventricular mass is most classic in the setting of death from acute hydrocephalus?

Answer 21

Colloid cyst which appears as a round, dense, mass at the foramen of monro that can cause acute obstruction of the foramen of monro causing acute hydrocephalus and, in extreme cases, death.

Question 22

What is the most common location for an intraventricular meningioma?

Answer 22

Trigone of the lateral ventricle (80% of intraventricular meningiomas are located here)

Question 23

Do pituitary adenomas enhance more rapidly or slower compared to normal brain?

Answer 23

Pituitary adenomas enhance more slowly compared to normal brain.

Question 24

What are common differences between craniopharyngiomas in an adult vs craniopharyngiomas in a child?

Answer 24

Adult: Papillary type which does not calcify. Is a capsulated lesion so is easier to resect. More solid lesion.

Peds: Adamantinomatous type which does calcify. May not be capsulated and is harder to resect. “Machinery oil” appearance. More cystic lesion.

Similarities: Both are partially solid and cystic lesions low grade lesions in sellar/suprasellar region.

Question 25

Meningiomas classically show uptake on what nuclear medicine studies?

Answer 25

Meningiomas typically have uptake with Tc-MDP (bone scan agent) and octreotide and Ga68-Dotatate.

Question 26

What are common differences between a CNS dermoid cyst and epidermoid cyst?

Answer 26

Epidermoid: can be congenital or acquired after LP/trauma. Usually located off of midline. Follow CSF intensity.

Dermoid: Typically located at midline with internal lipoid material, fat density on CT, bright on T1 weighted images, NF2 association.

Question 27

If you see what looks like a meningioma but there is associated bony invasion of the skull, what additional entity should be considered?

Answer 27

Hemangiopericytoma: a soft tissue sarcoma that can mimic an aggressive meningioma. These typically do not calcify or cause hyperostosis but these do often invade the calvarium. If you see invasion of the calvarium, imaging cannot differentiate between a meningioma or a hemangiopericytoma.

Question 28

In what age group to atypical teratoma/rhabdoid (AT/RT) tumors most commonly present?

Answer 28

Pediatrics, < 6 years of age and often < 2 years of age. AT/RT tumors are high grade often large tumors with internal necrosis and heterogeneous enhancement which may be in a supra- or infra-tentorial location but are most common in the cerebellum. Cannot tell difference on imaging between a medulloblastoma and AT/RT so this is a pathologic diagnosis.

Question 29

Are desmoplastic infantile gliomas more commonly supratentorial or infratentorial?

Answer 29

Desmoplastic infantile gliomas (DIGs) are classically supratentorial-only lesions. These are large, cystic tumors in a superficial cortical location. Commonly present with rapidly increasing head circumference before first birthday.

Question 30

What is the most common location of both a choroid plexus papilloma/carcinoma in pediatric patients and in adults?

Answer 30

Pediatrics: Supratentorial location in lateral ventricle.

Adults: Infratentorial location in 4th ventricle

Question 31

What is the most common brain metastasis in pediatric patients?

Answer 31

Neuroblastoma. Three common sites of metastatic disease with neuroblastoma are the bones, the dura/brain, and the posterolateral orbit.

Question 32

If you see a cyst with mural nodule in the temporal lobe of a teenager with epilepsy which tumors should you think of first?

Answer 32

First is probably a ganglioglioma which may present with a cystic and solid mass with calcifications essentially anywhere in any age range but classic is with a temporal lobe mass in setting of temporal lobe epilepsy. Differential includes other cortical based tumors; remember DOG for cortical-based tumors (DNET, Oligodendroglioma, Ganglioglioma). Note ganglioglioma is different from a desmoplastic infantile glioma and classic history for the latter is rapid head enlargement in a pediatric patient < 1 year of age). Note also that you can’t tell a DNET from a ganglioglioma on imaging.

Question 33

What is the most common location for a pleomorphic xanthroastrocytoma (PXA)?

Answer 33

PXA’s are always supratentorial, usually located in the temporal lobe, presenting with a cyst with mural nodule. This may have a dural tail and is also common in setting of seizures

Question 34

True or false: A PNET (primitive neuroectodermal tumor) appears similarly on histology as a medulloblastoma?

Answer 34

True. These entities can look very similar on histology. However, a PNET is a supratentorial lesion and have been nicknamed a “supratentorial medulloblastoma”. Bad prognosis with PNET due to propensity for distant metastases.

Question 35

What is the classic imaging appearance of a medulloblastoma?

Answer 35

Medulloblastomas commonly present as a midline mass centered at the roof of the 4th ventricle with associated hydrocephalus.

Question 36

What tumor is classically associated with gelastic seizures and precocious puberty, with a mass of the tuber cinereum?

Answer 36

Hypothalamic hamartoma. This is a hamartoma of the tuber cinereum. Typically, do not enhance. This is separate in location from the pituitary stalk.

Note—a gelastic seizure is a seizure with sudden onset of laughing or other sudden release of energy.

Question 37

What is more common in the spine—medulloblastoma or ependymoma?

Answer 37

Medulloblastoma is much more common than ependymoma. Medulloblastomas of the spine tend to restrict on DWI and have zuckerguss (sugar icing) appearance with leptomeningeal spread/coating of disease. Ependymomas are more likely to calcify than medulloblastomas

Question 38

Can you name at least one syndrome with a medulloblastoma association?

Answer 38

Perhaps top two are basal cell nevus syndrome (AKA Gorlin syndrome) which presents with medulloblastoma and dural calcifications, basal cell skin cancers, odontogenic cysts, common in postradiation state. Also, Turcot syndrome (discussed in episode 1) are classic for GI polyposis and brain tumor to include medulloblastoma and/or glioblastoma.

Question 39

With a vertical gaze palsy (aka dorsal Parinaud syndrome) what tumor is most classic?

Answer 39

A pineal tumor.

Question 40

What is the most common pineal tumor?

Answer 40

A germinoma is the most common pineal tumor (only classically seen in boys). In general, girls are much more likely to have suprasellar germinomas and boys are most likely to have pineal germinomas. Germinomas can cause precocious puberty via HCG secretion.

Question 41

Can you name some other pineal region tumors? What are some differences between these?

Answer 41

Besides pineal germinoma, there is also pineocytoma (uncommon in childhood, non-invasive, children “hide out of cyt (sight)”), pineoblastoma (common in childhood, “kids frequently have a blast”, highly invasive).

Question 42

What is the so-called “trilateral retinoblastoma”?

Answer 42

This is when you have bilateral retinoblastomas and a concurrent pineoblastoma as these tumors are associated with one another. Both are small round blue cell tumors.

Question 43

What is the significance of pineal calcifications in differentiating between a germinoma versus pineocytoma/pineoblastoma?

Answer 43

If pineal calcifications appear “exploded” it is a pineoBLASToma/cytoma. If pineal calcifications appear engulfed it is more likely a pineal germinoma.