Intracranial teratoma
Intracranial teratomas are uncommon intracranial neoplasms, which can have a bewildering variety of components and thus a wide range of appearances.
Epidemiology
Although uncommon in the general population, they account for the largest proportion of fetal intracranial neoplasms ( ~ 33 - 50 % of fetal brain tumours 3)
Clinical presentation
They are often detected antenatally or in the neonate.
Sometimes may be associated with elevated levels of
Pathology
They are comprised of cells originating from at least two and usually all three embryonic layers : ectoderm, mesoderm and endoderm. The histological sub type may not necessarily determine the biological behavior.
They are considered intracranial germ cell tumours, and can be divided into two broad categories : intra and extra axial.
Intra-axial
Intra axial teratomas, i.e. those located within the cerebral hemispheres, typically present either antenatally or in the newborn period. They are large tumours that increase head circumference and therefore often present with difficulty in child birth. They tend to more commonly occur supratentorially.
Extra-axial
Extra axial teratomas usually present in childhood or early adulthood and are typically smaller. They most commonly arise in the pineal or suprasellar regions.
Another method of classifying an intracranial teratoma is as
- mature
- immature
- with malignant transformation
Radiographic features
Intracranial teratomas are often seen as large lesions at presentation.
Given their extremely variable histological components, imaging also tends to be heterogenous, with tumours typically demonstrating a mixture of tissue densities and signal intensity. Fat, if present is helpful in narrowing the differential.
MRI brain
- T1 : heterogenous signal overall due to different components with fat components being notably high signal and calcific components being notably low
- T1 C+ (Gd) : solid soft tissue components show enhancement
- T2 : again mixed signal from differing components
Treatment and prognosis
Location determines prognosis. Stillbirth occurs in a majority of fetal cases 3.
Differential diagnosis
A meaningful differential would somewhat depend on location. Considerations include
- sPNET
- atypical rhabdoid / teratoid tumour (ATRT) : later age group
- intracranial lipoma : fatty components only
- intracranial dermoid : more mature tissue
- craniopharyngioma : partcularly for suprasellar lesions
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