Type:
Educational Exhibit
Keywords:
Pathology, Education and training, Diagnostic procedure, MR, CT, Neuroradiology brain
Authors:
S. Moawad1, S. Hasan2, H. Semaan3, S. pinsky2, H. Elsamaloty3; 1Toledo, Ohio/US, 2Toledo/US, 3Toledo, OH/US
DOI:
10.1594/ecr2018/C-1187
Findings and procedure details
Approach to pineal region masses:
1) Determine if the mass is pineal or extra-pineal in origin (Fig. 2)
- If the tumor is below these veins,
a suboccipital infratentorial approach.
- If the tumor is above these veins,
an interhemispheric or Sub temporal approach is used.
Fig. 2: Algorithmic approach toward pineal region lesions
2) Age of the patient
Fig. 3
3) Pattern of calcifications (if present)
Fig. 4: Patterns of calcification
4) Signal characteristic of the tumor on MRI
Pineal germ cell tumors:
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Intracranial germ cell tumors (iGCT) can be found in the pineal gland as well as other intracranial midline locations including the suprasellar region.
There is an association between iGCT and Down syndrome.
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They are thought to be due to aberrant migration of totipotent germ cells during early embryogenesis.
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Germinomas and teratomas are the most common types (Fig. 5).
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Serum and CSF values of certain tumor markers will help with the diagnosis of certain GCT (Fig. 6).
1) Germinoma ( Fig. 8,
Fig. 9 ):
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Synonyms: Dysgerminoma,
extra-gonadal seminoma,
atypical teratoma.
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Incidence: 1%–2% of all intracranial neoplasms.
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Age: 90% of patients < 20 years old.
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Sex: M/F ~ 10:1 (pineal region).
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Location:
~50–65% pineal
~25-35% suprasellar
- Malignant but relatively benign prognosis due to radiation and chemotherapy sensitivity.
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Prognosis: 5-year survival ~ 90%
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A tendency for CSF seeding and imaging of the entire neural axis is necessary when a germinoma is diagnosed.
Fig. 7: Imaging Characteristics of pineal germinoma
Fig. 9: Sagittal MRI T2WI (a) , T1WI (b) and T1WI+C (c) showing a T1 and T2 isointense germinoma with homogenous post contrast enhancement.
2) Teratoma:
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Age: Can be detected in utero and can lead to difficulty in childbirth or present as enlarged head circumference in a neonate
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Gender: Males > Females.
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Mature teratoma > fully differentiated.
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Immature/Malignant teratoma > resembles fetal tissues (not sensitive to chemotherapy or radiation).
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Prognosis: 5-year survival for malignant teratomas ~ 18%.
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May rupture causing chemical meningitis.
Fig. 10: Imaging characteristics for pineal teratoma.
Fig. 11: Axial CT image (a) showing a heterogenous pineal mass contain fat (arrowheads), soft tissue and calcifications.
Coronal T2WI (b) and axial T1WI+C (c) showing enhancing soft tissue component of the teratoma (arrowheads in c).
3) Yolk Sac (Endodermal Sinus) Tumor:
4) Choriocarcinoma:
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Primary intracranial choriocarcinoma is the rarest,
most malignant primary intracranial GCT.
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HCG/β-HCG levels are elevated.
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Poor prognosis due to their high risk for fatal hemorrhage and their propensity for extraneural/CSF metastasis.
Fig. 13: Table: Imaging Characteristics of pineal Choriocarcinoma.
Figure: Sagittal MRI T2WI shows a large, markedly heterogeneous mass centered at the pineal gland with areas of both hypointensity and hyperintensity reflecting the histologic heterogeneity, including hemorrhage, fibrosis, cysts, or necrosis with fluid-fluid level (blood)
5) Embryonal Carcinoma:
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Malignant tumor composed of undifferentiated epithelial cells.
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Typically part of a mixed germ cell tumor.
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Age: peripubertal patients.
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Gender: Slightly increased incidence in males.
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Pineal or suprasellar location.
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Aggressive tumor with local invasion and systemic metastatic potential.
Fig. 14: Imaging Characteristics of pineal embryonal Carcinoma
6) Mixed Cell tumor:
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Mixed tumor containing elements from all other germ cell tumors.
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When embryonal carcinoma is part of a mixed germ cell tumor,
it can be the most aggressive component and may be the only component to produce systemic metastases.
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Imaging characters are similar to embryonal cell carcinoma.
Fig. 15: Axial T2WI (a) and T1WI + C (b) shows mixed solid-cystic pineal region mass with heterogenous enhancement. This was proven to be a mixed germ cell tumor after surgery.
Pineal parenchymal Masses:
1) Pineoblastoma:
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Malignant lesions,
typically > 3 cm.
Nearly 100% present with hydrocephalus.
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Synonyms: primitive neuroectodermal tumor (PNET) of pineal gland.
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Age: children > young adults.
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Sex: M:F ~ 1:2
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CSF seeding common
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Prognosis: median survival 16-25% from the presentation.
Fig. 16: Table: Imaging characteristics of Pineoblastoma
Figure: A) Large heterogenous mass with “exploded”, peripheral calcification (arrowheads) with obstructive hydrocephalus (Image courtesy of James G. Smirniotopoulos, M.D)
B)Sagittal T1WI showing heterogenous pineoblastoma with areas of necrosis. Note the obstruction of the cerebral aqueduct (arrowhead), a common finding in pineoblastoma.
2) Pineocytoma:
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Benign lesions,
typically < 3 cm.
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Incidence: 0.4 – 1% of primary brain tumors; pineal parenchymal tumors are much less common than germinomas.
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Age: Peak incidence 10-20 years,
mean age 35 years (may occur at any age).
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Prognosis: Overall 5-year survival of 85%.
Fig. 17: Table: Imaging characteristics of Pineocytoma.
Figure: Axial CECT (a) showing homogenous enhancement of the pineocytoma. Axial T1WI (b) and axial T2WI (c) showing the pineoyctoma to be isointense to grey matter on T1 and hyperintense on T2.
3) Trilateral Retinoblastoma:
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Synchronous bilateral intraocular tumors observed in association with a PNET of the pineal or suprasellar region (80%).
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Locations: ~ 80% pineal tumor,
~ 20% suprasellar tumor.
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Inherited Rb (chromosome 13).
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1/3 inherited but 2/3 heritable.
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Look at orbits as well as the suprasellar region.
Fig. 18: Axial CECT images showing a trilateral retinoblastoma. Note the retinal calcifications in the right eye (black arrow) indicating a retinoblastoma. The left eye has been enucleated for a retinoblastoma. There is an associated enhancing pineal PNET ( white arrow).
4) Pineal Cyst:
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Incidence: 1-4% on imaging,
20-40% microscopic cysts found at autopsy.
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Age: mean age of 28 years
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Sex: F:M = 3:1
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Commonly measure 2-7 mm.
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Most cysts are asymptomatic and do not require treatment; however,
atypical lesions may require stereotactic aspiration.
Fig. 19: Table: Imaging characteristics of Pineal cyst
Figure: Sagittal T1WI (a), Axial T2WI (b) images showing a CSF signal intensity pineal cyst (arrow). Note the incomplete suppression on FLAIR (c).
Extra-pineal Masses:
1) Tectal Glioma:
- Typically low-grade astrocytomas with good prognosis,
unlike other childhood brainstem gliomas.
- Associated with NF1
- Expands tectum & obstructs cerebral aqueduct causing hydrocephalus.
However,
most will often need only CSF diversion without resection due to their indolent course.
Fig. 20: Table: Imaging Characteristics of tectal glioma.
Figure: Axial NECT (a) showing tectal glioma with calcifications. Sagittal T1WI (b) show the mass to be hypointense to GM with enhancement on axial T1WI +C (c) The avid enhancement is atypical and suggests a high grade glioma.
2) Thalamic Pilocytic Astrocytoma:
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Low-grade,
relatively well-defined astrocytomas (WHO Grade I).
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Tend to occur in young patients and have a relatively good prognosis.
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Pilocytic astrocytomas arising from the tectum characteristically manifest with headaches,
vomiting,
paresis,
abnormal gait,
somnolence,
Parinaud syndrome,
and diplopia.
Fig. 21: Sagittal (a) and axial (b) T1WI +C showing avidly enhancing right thalamic pilocytic astrocytoma mimicking a pineal mass.
3) Glioblastoma Multiforme (GBM):
Fig. 22: Tectal Glioblastoma Multiforme (GBM): Sagittal T1WI (a), sagittal T2wI and coronal T1WI +C show a heterogenous aggressive GBM resulting in obstructive hydrocephalus.
4) Vein of Galen Malformation (VGAM):
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Arteriovenous fistula (AVF) between deep choroidal arteries and embryonic median prosencephalic vein (MPV) of Markowski causing high flow through MPV which prevents formation of vein of Galen (VGAM is a misnomer).
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Most common antenatal diagnosed intracranial vascular malformation.
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The presentation is often with high-output cardiac failure in the neonatal period.
As much as 80% of cardiac output may shunt through the fistula.
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Ideally,
embolization is deferred until 6 months of age for choroidal VGM to allow the cavernous sinus to mature.
Fig. 23: A)Sagittal ultrasound Showing the vein of Galen malformation (VGAM) (arrows).
Brain MRI sagittal T1WC (B), T2W (C) and coronal T2W (D) demonstrating the VGAM (white arrows) and an associated hemorrhage (yellow arrow)
5) Pineal Region Lipoma:
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Synonym: Lipomatous hamartoma
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CNS Lipomas are congenital malformations and not true neoplasms.
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Usually incidental and asymptomatic
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Any Age
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M=F
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10-15% of intracranial lipomas are in the tectal region.
Fig. 24: Figure: Sagittal T1WI (a) shows well circumscribed hyperintense midline mass which demonstrates drop in signal on the axial T1-weighted fat saturated images (b) (arrow).