Atypical teratoid rhabdoid tumors (AT/RT) and ETMR

Atypical teratoid/rhabdoid tumors (AT/RT) and embryonal tumors with multilayered rosettes (ETMR) are embryonal tumors of the CNS that occur most commonly in infants and young children. AT/RT occurs sporadically or in a familial pattern due to mutation of SMARCB1 and is diagnosed by the loss of INI1 nuclear staining. ETMR includes embryonal tumors with abundant neuropil and true rosettes (ETANTR), ependymoblastomas, and medulloepitheliomas and is characterized by LIN28A positivity and amplification of the C19MC miRNA cluster. Staging for both AT/RT and ETMR includes MRI of brain and spine with CSF analysis, and initial therapy is typically maximal safe resection. Postoperative therapy may include chemotherapy and radiation, depending on the age of the patient and spread of the tumor. Detailed roles for surgery, chemotherapy, and radiation will be reviewed in this chapter, with an emphasis on the use of radiation to treat AT/RT and ETMR of the CNS.