CBMN is one of the radiologic patterns of central nervous system tumors.
In a classification of the patterns of contrast enhancement in the brain and meninges,
this one is considered a subtype of intra-axial enhancement lesions included in the category of fluid-secreting low-grade primary neoplasm.
The most common are: hemangioblastoma,
pilocytic astrocytoma,
ganglioglioma,
pleomorphic xanthoastrocytoma and,
as less common,
tanycytic ependymoma,
intraparenchymal schwannoma,
desmoplastic infantile ganglioglioma and cystic metastasis.
Other rare causes should be considered (infections or vascular anomalies).
Pilocytic astrocytoma
Formerly known as juvenile pilocytic astrocytoma,classified as World Health Organization (WHO) grade I,
it is a well-circumscribed,
often cystic,
slow-growing tumor. Pilocytic astrocytomas are tumours of young people,
with 75% occurring in the first two decades of life,
typically late in the first decade (9-10 years).
There is no recognised gender predisposition.There is a strong association with neurofibromatosis type 1 (NF1).
NF1 associated tumours have a tendency to affect the optic nerves and chiasm. Typically it presents as a cystic cerebellar CMNT or as an enlarged optic nerve/chiasm/tract with variable enhancement.
It is located in the cerebellum in 60% of cases.
The pilocytic astrocytoma derives from astrocytic precursor cells and it is the most common primary brain tumor in children.
Microscopically it shows classic biphasic pattern of two astrocyte populations: (a) compacted bipolar cells with Rosenthal fibers (Rosenthal fibers electron dense glial fibrillary acidic protein (GFAP) staining cytoplasmic inclusions); (b) loose-textured multipolar cells with microcysts,
eosinophilic granular bodies.
Immunohistochemistry reflects the astrocytic differentiation: GFAP: positive,S100: positive,OLIG2: positive, IDH R132H mutation: negative,p53 protein: negative or weak.
Differential diagnosis include: medulloblastoma,
atypicalteratoid/rhabdoid tumour,
ependymoma,
haemangioblastoma,
ganglioglioma,
pleomorphic xanthoastrocytoma.
Hemangioblastoma
Hemangioblastoma,
also named capillary hemangioblastoma,
is a vascular neoplasm of uncertain origin currently classified as a WHO grade I tumor.
It is found mostly in adults.
Slight male predilection in adults: M:F ratio of 1.3-2.6:1.
Peak incidence at around 30-60 years of age,
but earlier in patients with vHL (Von Hippel Lindau).
Sporadic cases make up approximately 75-80%,
with the remainder being found in patients with vHL.
Most frequently present with symptoms relating to: headaches: 70%, hydrocephalus and symptoms of raised intracranial pressure: 50 %,
cerebellar dysfunction: ~50-60%,
altered mental state: 10%,
polycythaemia due to erythropoietin production occurs in ~20% (range 5-40%) of cases.
It presents as a CMNT in 60% of cases with theenhancing mural nodule abutting the pia; in 95% of cases,
hemangioblastomas are in the posterior fossa,
predominantly in the cerebellar hemispheres.
The hemangioblastoma is a vascularized neoplasm with stromal cells of uncertain histogenesis.
Historically they were assigned in the category of vascular meningiomas although they gained an independent WHO category from 1991. Haemangioblastoma is actually a capillary haemangioma and,
despite the name with the affix of "blastoma",
it is a low grade (WHO grade I) lesion (note that the calvarial haemangioma is a cavernous haemangioma). The tumour is usually well circumscribed with a highly vascular mural nodule almost always abutting pial layer and a peripheral cyst which has similar contents as blood plasma.
Hence it is suggested that the cystic component most likely arises by exudation from the solid nodule vascular component. Regarding the pathogenesis of the formation of the cyst,
a major hypothesis is that the absence of astrocytic end feet and tight junctions can be found in the microvessels of these neoplasms,
which may lead to breakdown of the bloodbrain barrier,
and have a role in cyst formation.
The cystic fluid is xanthochromic,with a concentration of amino acids,
alkaline phosphates,and mucoproteins similar to blood,
suggesting that they originate by diffusion from the vascular component of the solid tumor.
Pleomorphic xanthoastrocytoma
Pleomorphic xanthoastrocytoma (PXA) is a WHO grade II distinct type of benign astrocytoma.
Typically it is a supratentorial cortical mass with an adjacent enhancing dural tail.
CBMN appearance is present in upwards of 60% of cases.
The temporal lobe is the most common location,
followed by the parietal and occipital lobes.They are rare tumours accounting for only 1% of primary brain tumours. Typically these tumours are found in young patients (children or young adults),
with a peak incidence in the second and third decade of life (10-30 years-of-age). As these tumours have a predilection for the temporal lobe,
they most frequently present with seizures (~ 75% of cases).
They usually present as cortical tumours with a cystic component and vivid contrast enhancement.
Features of slow growth may be present,
such as no surrounding oedema and scalloping of the overlying bone.
A reactive dural involvement expressed by a dural tail sign can be found.
Calcifications are rare. From a pathologic point of view,
the PXA is noted for cellular pleomorphism and xanthomatous change.
It may originate from cortical (subpial) astrocytes or from multipotential neuroectodermal precursor cells common to both neurons and astrocytes.
It has a pleomorphic appearance meaning that it can be highly variable in the size and shape of cells and/or their nuclei.
CD34 antigen may help differentiate PXA from other tumors and may be associated with cortical
dysplasia. Immunohistochemistry demonstrates expected glial marker reactivity.
Less obviously,
there is also variable reactivity for neuronal markers. GFAP: positive,
although often only weakly, S100: positive,
neuronal markers including synaptophysin, MAP2 and neurofilament: variable. Pleomorphic xanthoastrocytomas,
as well as pilocytic astrocytomas (and many non-CNS tumours),
exhibit BRAF mutations 6,7.
The only reported association is with neurofibromatosis type 1,
although this is not a strong association.
Although prognosis is good following surgical excision,
with a 5-year survival of 90% and 5-year-disease-free-survival of 70%.
Ganglioglioma
The ganglioglioma is a well-differentiated,
WHO grade I or II,
slow-growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells. In a minority of cases (5%) these tumours show aggressive behaviour and histopathologic features and are then called anaplastic gangliogliomas (WHO grade III).
At this stage,
no criteria for WHO II gangliogliomas have been established.
Typical features are a partially cystic component with an enhancing,
cortically based mass in a child/young adult with temporal lobe epilepsy.
.
Malignant transformation into glioblastoma multiforme has been reported.
There are two theories on the etiology of the ganglioglioma: (a) it may be a neoplastic transformation of glial hamartoma or (b) it may derive from subpial granule cell transformation.
Genetics: BRAF V600E mutations are encountered in 20-60% of cases. IDH: negative (if positive then the tumour is most likely a diffuse glioma).
Local resection is the treatment of choice and determines prognosis.
In the brain,
where a reasonable resection margin can be achieved,
the prognosis is good,
with recurrence-free survival reported to be 97% at 7.5-year follow-up.
Desmoplastic infantile ganglioglioma
Desmoplastic infantile ganglioglioma (DIG) is a WHO grade I tumor, slow growing glioneuronal tumours arising from either cortical or deep grey matter, that affects children in the first 2 years.
Boys are affected more commonly than girls. Symptoms of DIG are intracranial hypertension,
sunset eye,
enlarging head circumference,
bulging fontanels,
variable localizing signs,
including seizures,
or paresis.
From a pathologic point of view,
DIG has prominent desmoplastic stroma plus neoplastic astrocytes,
with a variable neuronal component.
DIG arises from subpial astrocytes; the large cyst contains xanthochromic fluid and the tumor may be firmly attached to the dura and brain tissue.
They demonstrate essentially no growth over time,
although very gradual increase in size has been described.
Only one case of malignant transformation has been reported.
Prognosis is excellent,
however,
due to the difficulty in managing seizure medically,
patients usually undergo resection and even in cases of incomplete resection,
seizures frequently cease.
Ependimoma
Represent a relatively broad group of glial tumours most often arising from the lining the ventricles of the brain or the central canal of the spinal cord. They account for ~5% of all neuroepithelial neoplasms,
~10% of all paediatric brain tumours and up to 33% of brain tumours occurring in those less than 3 years of age.
Posterior fossa: 60%.
There is no recognised gender predilection .
Although they can occur at any age,
the posterior fossa tumours tend to present more commonly in the paediatric age group (mean age at diagnosis is 6 years of age),
with a smaller second peak for supratentorial tumours around the 3rddecade.
Associations a neurofibromatosis type 2 (NF2).
Cystic meningioma
Meningiomas are common tumors of the central nervous system that account for approximately 15% of all intracranial tumors and are the most common extra-axial neoplasm (i.e.,
neoplasm that does not arise from the brain or spinal cord).
Th e WHO classifi es meningiomas into many diff erent subtypes based on histological parameters.
Of these subtypes,
transitional,
fi broblastic,
and meningothelial are the most common.
Histologically,
transitional meningiomas are characterized by whorl formation with closely wrapped cells.
Most meningiomas are benign neoplasms with a WHO grade 1 classifi cation.
Approximately 8% of meningiomas are considered “atypical” (WHO grade 2) and tend to have a higher incidence of recurrence (2).
Th e presence of necrosis,
excessive mitotic activity,
and evidence of brain invasion are histologic features that result in an “atypical” classifi cation.
Anaplastic meningiomas (WHO grade 3) account for <1% all meningiomas and have a much shorter mean survival time,
with a 5-year-survival rate of approximately 64%,
compared with 95% for atypical meningiomas.
“Benign” metastasizing meningiomas have also been reported,
but are rare
Metastases
Brain metastasis is the most common intracranial tumor in adults.
It presents clinically as headache,
seizures or loss of cognitive or motor function.
The incidence of brain metastasis is rising with the increase in survival of cancer patients.
Approximately,
20%-40% patients with cancer will develop brain metastases in the course of their disease.
A frank CBMN pattern in metastasis is rare.
Recently,
a case has been described in the literature.
Cystic metastasis is much more common.
Very rare cases
Tanycytic ependymoma
Intracerebral schwannoma
Rosette-forming glioneuronal tumor
(RGNT) of the fourth ventricle
Papillary glioneuronal tumor
Adjacent epidermoid cyst and primary
central nervous system lymphoma
Vascular lesions
Neurocysticercosis