Atypical teratoid/rhabdoid tumor

Last revised by Yuranga Weerakkody on 9 Jan 2024

Atypical teratoid/rhabdoid tumors (AT/RT) are uncommon WHO grade 4 tumors, 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 medulloblastoma by imaging and even H&E microscopy, and the diagnosis requires cytogenetic analysis of the tissue.

AT/RTs typically present in very young children (median age is less than 2-3 years 2,13).

Rhabdoid cells are the hallmark of AT/RT, but only comprise a fraction of the tumor and are not required for the diagnosis provided genetic of DNA-methylation changes are compatible (see below) 13.

Other portions of the tumor are indistinguishable on imaging and histology from a medulloblastoma or embryonal tumor with multilayered rosettes.

The vast majority (~95%) of AT/RTs have inactivation of both copies of SMARCB1 (also known as INI1, BAF47 or hSNF5). In a small minority of cases (< 5%) it is SMARCA4 (also known as BRG1) that is inactivated 13

Additionally, AT/RTs can be divided into three subgroups according to DNA-methylation profiling: AT/RT-SHH, AT/RT-TYR, and AT/RT-MYC 13.

To make the diagnosis, either SMARCB1 or SMARCA4 mutations or compatible DNA-methylation profiling need to identified 13

Rhabdoid cells usually demonstrate:

  • EMA: positive

  • vimentin: positive

  • SMA (smooth muscle actin): positive

Atypical teratoid/rhabdoid tumors are usually large and very heterogeneous masses. They may be difficult to distinguish from an embryonal tumor with multilayered rosettes by imaging.

  • infratentorial: ~50%

    • cerebellum (most common)

    • brainstem

  • supratentorial

  • 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 hemorrhage:

  • T1: iso- to slightly hyperintense to grey matter (hemorrhagic areas can be more hyperintense)

  • T2: generally hyperintense (hemorrhagic areas can be hypointense)

  • T1 C+ (Gd): heterogeneous enhancement

  • MR spectroscopy

    • Cho: elevated

    • NAA: decreased

  • DWI

    • 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.

Surgery with debulking can be offered in some cases. Tumors can demonstrate leptomeningeal dissemination. Clinically AT/RTs have a much poorer prognosis than medulloblastomas, with little if any response to chemotherapy and death usually occurring within a year of diagnosis. 

Primary CNS rhabdoid tumor was first identified as a unique entity in the mid/late 1980s. Prior to this, these tumors were likely misdiagnosed as primitive neuroectodermal tumor/medulloblastoma, as they are relatively similar in microscopic appearance 12. Early reports variably used the term malignant rhabdoid tumor.

Imaging differential considerations include:

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