Atypical teratoid/rhabdoid tumours (AT/RT) 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/RT often resembles PNET by imaging and even H&E microscopy, and the diagnosis requires cytogenetic analysis of the tissue.
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).
Rhabdoid cells are the hallmark of AT/RT, but only comprise a fraction of the tumour. Other portions of the tumour are indistinguishable on imaging and histology from a medulloblastoma or supratentorial primitive neuroectodermal tumour (PNET).
According to 2016 WHO classification scheme, a diagnosis of AT/RT requires confirmation of specific genetic aberration (loss of INI1 tumour suppressor gene on chromosome 22 or BRG1 gene); otherwise, a descriptive diagnosis of CNS embryonal tumour with rhabdoid features is used 8,10.
Atypical teratoid/rhabdoid tumour are usually large and very heterogeneous masses. They may be difficult to distinguish from a PNET by imaging.
- infratentorial: ~50%
- cerebellum (most common)
- cerebral hemispheres
- pineal gland region (see pineal mass differential diagnosis)
- septum pellucidum
- often isodense to grey matter
- may demonstrate heterogeneous enhancement
- calcification is common
- may show associated obstructive hydrocephalus
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
- Cho: elevated
- NAA: decreased
- almost all restrict diffusion
Leptomeningeal seeding has been described in up to 15-30% of cases and so post-contrast imaging of the entire neuroaxis should be considered in suspected AT/RTs.
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.
History and etymology
Primary CNS rhabdoid tumour was first identified as a unique entity in the mid/late 1980's. Prior to this, these tumours were likely misdiagnosed as primitive neuroectodermal tumour/medulloblastoma, as they are relatively similar in microscopic appearance 12. Early reports variably used the term malignant rhabdoid tumour.
Imaging differential considerations include:
- 1. Barkovich AJ. Pediatric neuroimaging. Lippincott Williams & Wilkins. (2005) ISBN:0781757665. Read it at Google Books - Find it at Amazon
- 2. Meyers SP, Khademian ZP, Biegel JA et-al. Primary intracranial atypical teratoid/rhabdoid tumors of infancy and childhood: MRI features and patient outcomes. AJNR Am J Neuroradiol. 2006;27 (5): 962-71. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Lee YK, Choi CG, Lee JH. Atypical teratoid/rhabdoid tumor of the cerebellum: report of two infantile cases. AJNR Am J Neuroradiol. 2004;25 (3): 481-3. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 4. Arslanoglu A, Aygun N, Tekhtani D et-al. Imaging findings of CNS atypical teratoid/rhabdoid tumors. AJNR Am J Neuroradiol. 2004;25 (3): 476-80. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 5. Han L, Qiu Y, Xie C et-al. Atypical teratoid/rhabdoid tumors in adult patients: CT and MR imaging features. AJNR Am J Neuroradiol. 2011;32 (1): 103-8. doi:10.3174/ajnr.A2361 - Pubmed citation
- 6. Koral K, Gargan L, Bowers DC et-al. Imaging characteristics of atypical teratoid-rhabdoid tumor in children compared with medulloblastoma. AJR Am J Roentgenol. 2008;190 (3): 809-14. doi:10.2214/AJR.07.3069 - Pubmed citation
- 7. Agrawal, Amit, et al. "Early Childhood Paraspinal Atypical Teratoid/Rhabdoid Tumor: Failure of Standard Treatments." Pediatric Cancer, Volume 4. Springer Netherlands, 2013. 195-198.
- 8. Judkins AR, Burger PC, Hamilton RL et-al. INI1 protein expression distinguishes atypical teratoid/rhabdoid tumor from choroid plexus carcinoma. J. Neuropathol. Exp. Neurol. 2005;64 (5): 391-7. Pubmed citation
- 9. Ahitagni Biswas, Lakhan Kashyap, Aanchal Kakkar, Chitra Sarkar, Pramod Kumar Julka. Atypical teratoid/rhabdoid tumors: challenges and search for solutions. (2016) Cancer Management and Research. 8: 115. doi:10.2147/CMAR.S83472 - Pubmed
- 10. David N. Louis, Arie Perry, Guido Reifenberger, Andreas von Deimling, Dominique Figarella-Branger, Webster K. Cavenee, Hiroko Ohgaki, Otmar D. Wiestler, Paul Kleihues, David W. Ellison. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. (2016) Acta Neuropathologica. 131 (6): 803. doi:10.1007/s00401-016-1545-1 - Pubmed
- 11. D. M.-T. Ho, C.-Y. Hsu, T.-T. Wong, L.-T. Ting, H. Chiang. Atypical teratoid/rhabdoid tumor of the central nervous system: a comparative study with primitive neuroectodermal tumor/medulloblastoma. (2016) Acta Neuropathologica. 99 (5): 482. doi:10.1007/s004010051149 - Pubmed
- 12. Lucy Balian Rorke,, Roger J. Packer,, Jaclyn A. Biegel. Central nervous system atypical teratoid/rhabdoid tumors of infancy and childhood: definition of an entity. (2009) Journal of neurosurgery. 85 (1): 56-65. doi:10.3171/jns.1996.85.1.0056 - Pubmed