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Atypical Teratoid/Rhabdoid Tumour (AT/RT)

Summary

  • Rare, highly aggressive embryonal tumour of the central nervous system (CNS)
  • Primarily affects young children, typically under 3 years of age
  • Characterised by loss of INI1/SMARCB1 gene expression and distinctive imaging features1

Pathophysiology

  • Arises from embryonal cells in the CNS
  • Defined by biallelic inactivation of SMARCB1 gene (95% of cases) or SMARCA4 gene (2% of cases)
  • Loss of these genes leads to dysregulation of chromatin remodelling and cell cycle control
  • Histologically heterogeneous, containing rhabdoid cells, primitive neuroectodermal cells, and mesenchymal elements

Demographics

  • Accounts for 1-2% of paediatric brain tumours
  • Median age at diagnosis: 17 months
  • Slight male predominance (1.6:1)
  • Rare cases reported in adults

Diagnosis

  • Clinical presentation:
  • Rapid onset of neurological symptoms
  • Increased intracranial pressure
  • Focal neurological deficits
  • Laboratory findings:
  • CSF cytology may show malignant cells
  • Histopathology:
  • Characteristic loss of INI1/SMARCB1 protein expression on immunohistochemistry
  • Presence of rhabdoid cells with eccentric nuclei and eosinophilic cytoplasmic inclusions

Imaging

  • CT:
  • Hyperdense, heterogeneous mass
  • Often with areas of haemorrhage and necrosis
  • Calcifications in 40-60% of cases
  • MRI:
  • T1: Heterogeneous, predominantly iso- to hypointense
  • T2: Heterogeneous, predominantly hyperintense
  • T1 post-contrast: Heterogeneous enhancement
  • DWI: Restricted diffusion in solid components
  • MR spectroscopy: Elevated choline, reduced NAA, presence of lipid/lactate peaks
  • Location:
  • 50-60% infratentorial (cerebellum, brainstem)
  • 40-50% supratentorial
  • Rarely in the spinal cord
  • Distinctive features:
  • "Cyst and nodule" appearance in some cases
  • Frequent leptomeningeal dissemination at diagnosis (20-30%)

panels-1

  • A 15-year-old patient presenting with seizures and headache.
  • CT showed only subtle hyperdensity in the left anterior temporal lobe and surrounding sulci.
  • MRI showed an heterogeneously enhancing tumour in the left anterior frontal lobe with extensive leptomeningeal disease in the anterior, middle and posterior cranial fossae.

Treatment

  • Multimodal: maximal safe resection, intensive chemotherapy and craniospinal irradiation (usually deferred in children under 3)
  • Prognosis is poor, though better with older age, gross total resection and localised disease

Differential diagnosis

Imaging differential Differentiating feature
Medulloblastoma Midline fourth-ventricular mass, more homogeneous with uniform restricted diffusion; AT/RT is more often off-midline/CPA and heterogeneous with haemorrhage
Ependymoma "Plastic" tumour extruding through the fourth-ventricular outlets; less haemorrhage
Choroid plexus carcinoma Avidly enhancing intraventricular frond-like mass with brain invasion
Embryonal tumour with multilayered rosettes (ETMR) Large, bulky supratentorial mass; overlapping imaging, distinguished by C19MC amplification
Pilocytic astrocytoma Cyst-with-enhancing-nodule, facilitated (not restricted) diffusion

  1. Richardson et al. Atypical Teratoid Rhabdoid Tumour : From Tumours to Therapies. 2018. Journal of Korean Neurosurgical Society - Open in new tab. ↩