Chapter 5 - Central Nervous System Neoplasm and Tumor-like Masses Flashcards
Clinical presentations of CNS neolplasm. (3)
- Headaches
- Seizures
- Focal neurological deficits
Study of choice for the evaluation of a patient with intracranial neoplasm.
Contrast- enhanced brain MRI
Basic sequences of MRI for evaluation of intracranial neoplasm (4)
- DWI
- T2WI (with FLAIR)
- T2*-weighted imaging (GRE or SWI)
- Pre/postcontrast T1WI
Advance options:
- Perfusion-weighted imaging
- MR spectroscopy
Restricted diffusion in DWI may be seen in what cases? (3)
- Acute stroke
- Hypercellar tumors (lymphoma)
- Highly viscous fluids
This measures cerebral blood volume (CBV) as a noninvasive marker of tumor vascularity, which usually increases with tumor grade
MR perfusion
This measures chemical shift of nonwater molecules in a region of interest (single or multi voxel) as a noninvasive marker of tumor metabolism.
MR spectroscopy
The chemical or frequency shift (in MRS) is measured how?
It is measures in parts per million (ppm), calibrated relative to tetramethysilane (TMS)
In a normal brain, what are the main metabolites and their respective peaks? (3)
- Choline - 3.2 ppm
- Creatine - 3.0 ppm
- N-acetylaspartate - 2.0 ppm
What choline/creatine ratio is suggestive of a high grade tumor?
Choline/creatine ratio >2
Uses of PET in CNS tumor
Distinguishing residual/recurrent tumor from radiation-induced changes in the white matter.
Tumors that metastasize to the brain that causes hemorrhage. (6)
- Melanoma
- Renal cell carcinoma
- Choriocarcinoma
- Thyroid carcinoma
- Breast carcinoma
- Bronchogenic carcinoma (lung)
(MR CT BB)
Calcified intracranial masses. (6)
- Craniopharyngioma
- Astrocytoma, aneurysm
- Chorid plexus tumor
- Oligodendroglioma (>50%)
- Meningioma
- Ependymoma
(CA COME)
Vascularized granulation tissue develops within how many hours following surgery and enhances after administration of contrast.
48 to 72 hours
The ideal time to obtain a post-operative contrast-enhanced study (usually MR)
These tumors account for the majority of all gliomas
Astrocytoma
approximately 75%
Astrocytomas and gliomas are divided into two major groups based on growth pattern.
- Circumscribed
2. Diffuse
These gliomas demonstrate more well-defined margins on micrscopic examination and tend to be more amendable to a surgical cure.
Circumscribed gliomas
- Lower grade and younger age
These gliomas demonstrate more ill-defined margins on microscopic examination, regardless of the macroscopic appearance on cross-sectional imaging.
Diffuse or infiltrative
Most common pediatric CNS tumor
Pilocytic astrocytoma
Most common location of pilocytic astrocytoma
- Cerebellum (60%)
followed by the:
- Optic pathways/ hypothalamus (30%)
- Brainstem
Most common age group of pilocytic astrocytoma
Children (<20 years old)
True or fase
Pilocytic astrocytoma is associated with neurofibromatosis type 1
True
A circumscribed astrocytoma that is less common and more aggressive variant of pilocytic astrocytoma
Pilomyxoid astrocytoma
Most commonly occures in the suprasellar region
A circumscribed astrocytoma that is slow-growing tumor located at the foramen of Monro and is associated with tuberous sclerosis
Subependymal giant cell astrocytoma
A circumscribed astrocytoma that is peripherally located cerebral tumor that often involves the cortex/ meninges.
Pleomorphic xanthoastrocytoma
Imaging pattern of circumscribed astrocytoma
- Circumscribed enhancing mass,
2. which may be accompanied by internal or adjacent fluid-filled cysts.
Classic appearance of a pilocytic astrocytoma in a child
Nonenhancing cyst with enhancing mural nodule in the cerebellum
This is a low-grade astrocytic tumor with low-level proliferative activity.
Diffuse astrocytoma
Astrocytic tumor with increased cellularity, mitotic activity, or nuclear atypia
Anaplastic Astocytoma
WHO genetically divides diffuse gliomas into: (2)
- Isocitrate dehydrogenase (IDH) mutant
2. Isocitrate dehydrogenase (IDH) wildtype
Which has better prognosis:
A. Isocitrate dehydrogenase (IDH) mutant
B. Isocitrate dehydrogenase (IDH) wildtype
A. Isocitrate dehydrogenase (IDH) mutant
Majory of diffuse and anaplastic astrocytoma are IDH- mutant
Imaging pattern of diffuse and anaplastic astrocytoma (4)
- Expansile parenchymal lesion
- Hypodense on CT
- Hyperintense on T2W
- Without significant enhancement (intact blood-brain barrier)
It may not be possible to distinguish diffuse from anaplastic astrocytoma before biopsy.
What are the possible clues to include the latter?
- Older age (>40 years old)
- Imaging markers:
- increased cellularity (decreased diffusion)
- mitotic activity (increased choline)
- tumor vascularity (increased perfusion)
This is a Grade IV or malignant astrocytoma and is overall the most common primary intra-axial tumor of the CNS.
Glioblastoma multiforme
It accounts for over hald of gliomas (55%)
Vast majority of glioblastoma are:
a. IDH-mutant
b. IDH-wildtype
b. IDH-wildtype
(90%), also known as primary glioblastomas
IDH-mutant (<10%) - also known as secondary glioblastomas - younger adults - less aggressive
Imaging pattern of glioblastoma (3)
- Heterogenously enhancing parenchymal mass with surrounding vasogenic edema.
- May include calcification or hemorrhage
- Can present as a single enhancing mass, multifocal enhancing masses, or a combination of both enhancing and nonenhancing tumor
Differential diagnosis for ring enhancing lesions (7)
- Metastasis
- Abscess
- Glioma (especially glioblastoma)
- Infarct (subacute or healing phase)
- Contusion/ hematoma (subacute)
- Demyelinating disease
- Radiation necrosis
(MAGIC DR)
Diffuse or infiltrative glioma (commonly glioblastoma) crosses the corpus callosum to involve both cerebral hemispheres
Butterfly glioma
In adults - this refers to either a diffuse infiltrative glioma, similar to supratentorial diffuse gliomas but in a less common location, or focal tectal glioma, which is a low-grade tumor in the midbrain that causes obstructive hydrocephalus
Brainstem glioma
In young children - this refers to a diffuse infiltrative glioma with highly aggressive behavior, despite absent or minimal enhancement.
Brainstem glioma or diffuse intrinsic pontine glioma
This describes widespread infiltrative growth of a diffuse glioma, more commonly astrocytoma than oligodendroglioma, to involve at least three lobes of the brain.
Gliomatosis cereberi
Less common and account for only 6% of all gliomas.
Demonstrate diffuse growth pattern, just like their astrocytic counterparts, with neoplastic cells infiltrating beyong the macroscopic margins of the tumor.
Oligodendrogliomas
Imaging pattern of oligodendroglioma (9)
- Expansile infiltrative parenchymal elsions
- Hypodense on CT
- Hyperintense on T2
- Most commonly located in the frontal lobes
- Extend peripherally to involve cortex
- More likely to exhibit calcification on CT
- Poorly defined margin - heterogeneous signal on MRI
- Vascular - Variable enhancement
It may not be possible to distinguish oligodendroglioma from anaplastic oligodendroglioma.
What possible clues to include the latter?
- Older age (>40 years old)
- Imaging markers:
- increased cellularity (decreased diffusion)
- mitotic activity (increased choline)
- tumor vascularity (increased perfusion)
These arise from the ependymal cells lining the ventricular system and the central canal of the spinal cord, therefore often present as a fourth ventricular mass in children, less commonly as an intramedullary mass in adults.
Ependymomas
Imaging pattern of ependymoma (6)
- Heterogeneous enhancing mass within the fourth ventricle in a child (most common)
- Capable of paraventricular or transependymal invasion into the brain parenchyma
- Heterogenous on CT
- Intratumoral calcification
- Cystic change
- Hemorrhage
Less common sites of ependymoma
- Cerebellopontine angles
- Cerebral hemispheres
- Lateral-third ventricles
Immediately underneath the ependymal lining of the ventricular system lies a thin subependyma glial plate. What tumor arise from this region?
Subependymoma
Most common locations of subependymoma (3)
- Inferior fourth ventricle
- lateral-third ventricles
- spinal cord
Difference of subependymoma from ependymoma
- Older adults (>40 years old)
2. Hypovascular - show less enhancement on post contrast imaging
Choroid plexus tumors occur on what age group?
Children (<20 years old)
Spectrum of choroid plexus tumor (3)
- Choroid plexus papilloma
- Atypical choroid plexus papilloma
- Choroid plexus carcinoma
Imaging pattern of choroid plexus tumor (2)
- Intensely enhancing masses with lobulated margins
2. Usually centered at the atrium or trigone of the lateral ventricle (arising from the choriod plexus glomus)
These tumors are characterized by varying degrees of neuronal differentiation (neurocytes and ganglion cells), often with glial component too.
Neuronal and mixed neuronal-glial tumors.
- Generally present in children or young adults (age <40 years old)
- 1% of all primary CNS tumor
This is a benign mixed neuroal-glial tumor with an excellent prognosis, associated with medically refrarctory partial complex seizures in children or yound adults.
Dysembryoplastic Neuroepithelial Tumor (DNET)
Typically imaging pattern of DNET
Nonenhancing multycystic (bubbly) mass at the cerebral cortex in a young patient, usually the temporal lobe