Intracranial teratomas are uncommon intracranial neoplasms, which can have a bewildering variety of components and thus a wide range of appearances. They can be divided into two broad categories, intra- and extra-axial, which differ in epidemiology and clinical presentation. Another method of classifying an intracranial teratoma is as mature, immature and mature with malignant transformation.
Although uncommon in the general population, they account for the largest proportion of fetal intracranial neoplasms (26-50% of fetal brain tumors ).
Clinical presentation varies according to whether they are intra- or extra-axial.
Intra-axial teratomas typically present either antenatally or in the newborn period. They are large tumors that increase head circumference and therefore often present with difficulty in childbirth. They tend to occur more commonly supratentorially.
Extra-axial teratomas usually present in childhood or early adulthood and are typically smaller. They most often arise in the pineal or suprasellar regions, and present due to the mass effect: obstructive hydrocephalus due to impingement on the midbrain, Parinaud syndrome, optic chiasm compression, etc.
Teratomas are considered intracranial germ cell tumors, and are comprised of cells originating from at least two and usually all three embryonic layers: ectoderm, mesoderm and endoderm. The histological subtype may not necessarily determine the biological behavior.
Sometimes may be associated with elevated levels of:
Intracranial teratomas are often seen as large lesions at presentation.
Given their extremely variable histological components, imaging also tends to be heterogeneous, with tumors typically demonstrating a mixture of tissue densities and signal intensity. Fat, if present, is helpful in narrowing the differential.
The majority of intracranial teratomas demonstrate at least some fat and some calcification, which is usually solid / "clump-like" . They usually have cystic and solid components, contributing to an irregular outline. Solid components demonstrate variable enhancement .
- hyperintense components due to fat and proteinaceous/lipid-rich fluid
- intermediate components of soft tissue
- hypointense components due to calcification and blood products
- T1 C+ (Gd): solid soft tissue components show enhancement
- T2: again mixed signal from differing components
Treatment and prognosis
Location and size determine prognosis:
- intra-axial (fetal) lesions: stillbirth occurs relatively frequently, and difficulty with vaginal delivery (if attempted) can occur due to enlarged cranial circumference
- extra-axial lesions: largely depends on the size and location; smaller lesions can be successfully resected with good prognosis
A meaningful differential depends to a degree on location: