Atypical teratoid/rhabdoid tumour

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.

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).

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
  • EMA: positive
  • vimentin: positive
  • smooth muscle actin: positive=

Atypical teratoid/rhabdoid tumour are usually large and very heterogeneous masses. 

Location
  • infratentorial: ~50%
    • cerebellum (most common)
    • brainstem
  • supratentorial
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

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. 

Imaging differential considerations include:

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Article Information

rID: 5897
Section: Pathology
Synonyms or Alternate Spellings:
  • Atypical teratoid / rhabdoid tumour
  • Atypical teratoid / rhabdoid tumour (AT/RT)
  • Atypical teratoid / rhabdoid tumor
  • ATRT
  • Atypical teratoid / rhabdoid tumours
  • Atypical teratoid - rhabdoid tumour

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