Atypical teratoid/rhabdoid tumor
Updates to Article Attributes
Atypical teratoid/rhabdoid tumours (AT/RTs) are an uncommon WHO Grade IV tumour, which in the vast majority of cases occurs in young children less than two years of age. It most frequently presents as a posterior fossa mass.
AT/RTs were until relatively recently classed as medulloblastomas, although both clinically and histologically they are different entities.
Epidemiology
They present in young children (median age is less than 2-3 years 2), whereas medulloblastomas typically occur in mid-childhood (median age 6 years).
Pathology
Microscopic features
Rhabdoid cells are the hallmark of AT/RT which however make up only a tiny fraction of the tumour, which is otherwise indistinguishable on imaging and histology from a medulloblastoma or supratentorial PNET. However, almost all AT/RTs show loss of INI1 tumour suppressor gene on chromosome 22 which distinguishes them from other entities 8.
Immunophenotype
Radiographic features
Atypical teratoid/rhabdoid tumour are usually large and very heterogeneous masses.
Location
- infratentorial: ~50%
- cerebellum (most common)
- brainstem
- supratentorial
- cerebral hemispheres
- pineal gland region (see pineal mass differential diagnosis)
- septum pellucidum
- hypothalamus
CT
- often isodense to gray matter
- may demonstrate heterogeneous enhancement
- calcification is common
- may show associated obstructive hydrocephalus
MRI
Can show necrosis, multiple foci of cyst formation and sometimes haemorrhage:
- T1: iso- to slightly hyperintense to grey matter (haemorrhagic areas can be more hyperintense)
- T2: generally hyperintense (haemorrhagic areas can be hypointense)
- T1 C+ (Gd): heterogeneous enhancement
-
MR spectroscopy
- Cho: elevated
- NAA: decreased
Treatment and prognosis
Surgery with debulking can be offered in some cases. Tumours can demonstrate leptomeningeal dissemination. Clinically AT/RTs have much poorer prognosis than medulloblastomas, with little if any response to chemotherapy, and death usually occurring within a year of diagnosis.
Differential diagnosis
Imaging differential considerations include:
- supratentorial CNS PNET: particularly for supratentorial ATRTs
-
medulloblastoma: tends to occur in an older age group 6.
CPAcerebellopontine angle involvment is rare. - intracranial teratoma
-<a href="/articles/medulloblastoma">medulloblastoma</a>: tends to occur in an older age group <sup>6</sup>. CPA involvment is rare.</li>- +<a href="/articles/medulloblastoma">medulloblastoma</a>: tends to occur in an older age group <sup>6</sup>. cerebellopontine angle involvment is rare.</li>
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